Vicor VI-J00 User Manual

Design Guide & Applications Manual

For VI-200 and VI-J00 Family DC-DC Converters
and Configurable Power Supplies

Design Guide & Applications Manual

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Table of Contents

VI-/MI-200 and VI-/MI-J00 DC-DC Converters Section Page(s)

Zero-Current-Switching 12

DC-DC Converter Pinouts 23

Module Do’s and Don’ts 3 4 – 6

vercurrent Protection

O

4

7

Output Voltage Trimming 5 8 – 10

Multiple GATE IN Connections 6 11

Application Circuits / Converter Array Design Considerations 7 12 – 13

Using Boosters and Parallel Arrays 8 14 – 17

EMC Considerations 9 18 – 28

Optional Output Filters 10 29

Battery Charger (BatMod) 11 30 – 32

Filter & Front-End Modules

AC Input Module (AIM / MI-AIM) 12 33 – 36

Harmonic Attenuator Module (HAM) 13 37 – 42

Input Attenuator Module (IAM / MI-IAM) 14 43 – 46

Ripple Attenuator Module (RAM / MI-RAM) 15 47

Offline Front End 16 48 – 51

Configurable Products

DC Input Power System (ComPAC / MI-ComPAC Family) 17 52 – 54

AC Input Power System (FlatPAC Family) 18 55 – 57

AC Input Power System (PFC FlatPAC) 19 58 – 59

General

Thermal and Module Mounting Considerations 20 60 – 67

Thermal Curves 21 68 – 77

Lead Free Pins (RoHS) 22 78 – 82

Tin Lead Pins 23 83 – 87

Module Packaging Options (SlimMod, FinMod, BusMod and MegaMod Families) 24 88

Product Weights 25 89

Glossary of Technical Terms 26 90 – 97

: This Design Guide and Applications Manual does NOT address Vicor’s Maxi, Mini and Micro DC-DC

NOTE
converters. For more information on these products go to vicorpower.com .

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 1 of 98

Apps. Eng. 800 927.9474 800 735.6200

Referen ced
to –Vin

[a]

Not in VI-J00 Series

Gate
Out

Vs

Vout

Vin

Ip

Vp

2.5 V
REF.

Output Filter

Integrator

Vs

Ip
Vp

MOSFET

Input
Filter

OC2

OC1

[a]

–S

TRIM

+S

E/A

+

+

–

+Vout

–Vout

Co

Lo

C

D2

D1

Reset

Control

GATE

IN

-Vin

+Vin

Logic

Control

Load

C/L

OTS

[a]

OVP

[a]

GATE

OUT

–

T1

1. Zero-Current-Switching

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

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Design Guide & Applications Manual

OVERVIEW

Vicor offers RoHS compliant modules. These modules have
a “VE” prefix. The information presented herein applies to
both versions, and “VI” will be the default designation.

he heart of Vicor’s VI-/ MI-200 and VI-/ MI-J00 module

T
technology, zero-current-switching, allows Vicor
converters to operate at frequencies in excess of 1 MHz,
with high efficiency and power density. Depending on
input voltage and load, the converters operate at
frequencies ranging from the low hundreds of kilohertz
(light load, high line) to approximately one megahertz (full
load, low line). Another aspect of the Vicor topology is
that two or more power trains driven at the same
frequency will inherently load-share if their outputs are
tied together. Load sharing is dynamic and is within 5%.
The VI-200 and MI-200 product line offer both Driver and
Booster modules:

• Drivers and Boosters must have identical power trains.

• Drivers close the voltage loop internally, Boosters do not.

• Boosters may be slaved to a Driver, allowing
configurations of multi-kilowatt arrays, which
exhibit dynamic current sharing between modules.

• Only a single control connection is needed between
modules with all module’s power inputs and outputs,
connected together — no trimming, adjustments, or
external components are required to achieve load sharing.

LOSSLESS ENERGY TRANSFER

Referring to Figure and Table 1–1 below, turn-on of the
MOSFET switch transfers a quantized energy packet from
the input source to an LC “tank” circuit, composed of
inherent transformer leakage inductance of T1 and a
capacitive element, C, in the secondary. Simultaneously,
an approximately half-sinusoidal current flows through the
switch, resulting in switch turn-on at zero current and
turn-off when current returns to zero. Resonance, or
bidirectional energy flow, cannot occur because D1 will
only permit unidirectional energy transfer. A low-pass filter
(Lo, Co) following the capacitor produces a low ripple DC
output. The result is a virtually lossless energy transfer
from input to output with greatly reduced levels of
conducted and radiated noise.

Ip: Primary current

Vp: Primary voltage

Vs: Secondary voltage

OVP: Overvoltage protection (output)

OTS: Over temperature shutdown

OC1, OC2: Opto-coupler

E/A: Error amplifier

REF: Bandgap reference

C/L: Current limit amplifier

Table 1–1

Apps. Eng. 800 927.9474 800 735.6200

Figure 1–1 — VI-/MI-200 and VI-/MI-J00 series zero-current-switching block diagram

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 2 of 98

Design Guide & Applications Manual

GATE
IN

G

ATE

OUT

+IN

–

OUT

–S

T

+S

+OUT

GATE
IN

GATE
OUT

+IN

–OUT

–S

T

+S

–IN

–IN

+OUT

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

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Figure 2–1 — VI-/MI-200, VI- / MI-J00

–IN, + IN. DC voltage inputs. See Tables 2–1 and 2–2 for
nominal input voltages and ranges for the VI-/MI-200 and
VI-/MI-J00 Family converter modules (data sheets contain
Low Line, 75% Max. Power and Transient ratings).

VI-200, VI-J00 Input Voltage Ranges

Designator Low Nominal High

0 10 V 12 V 20 V
V 10 V12/24 V 36 V
1 21 V 24 V 32 V

W 18 V 24 V 36 V

2 21 V 36 V 56 V
3 42 V 48 V 60 V
N 36 V 48 V 76 V
4 55 V 72 V 100 V
T 66 V 110 V 160 V
5 100 V 150 V 200 V
6 200 V 300 V 400 V
7 100 V 150/300 V 375 V

Table 2–1 — VI-200, VI-J00 input voltage ranges

MI-200, MI-J00 Input Voltage Ranges

Designator Low Nominal High

2 18 V 28 V 50 V
5 100 V 155 V 210 V
6 125 V 270 V 400 V
7 100 V 165 V 310 V

Table 2–2 — MI-200, MI-J00 input voltage ranges

2. DC-DC Converter Pinouts

GATE IN. The GATE IN pin on a Driver module may be
used as a logic Enable / Disable input. When GATE IN is
pulled low (<0.65 V @ 6 mA, referenced to –Vin), the

odule is turned off; when GATE IN is floating (open

m
collector), the module is turned on. The open circuit

oltage of the GATE IN pin is less than 10 V.

v

–OUT, +OUT. DC output pins. See the Table 2–3 and 2–4
below for output voltages and power levels of VI-/MI-200
and VI-/MI-J00 Family converter modules.

VI-200, VI-J00 Standard Output Voltages

Designator Output Designator Output

Z2V 215 V
Y 3.3 VN18.5 V
05V 324 V
X 5.2 VL28 V

W 5.5 VJ36 V

V 5.8 VK40 V
T 6.5 V448 V
R 7.5 VH52 V

M 10 VF72 V

1 12 VD85 V
P 13.8 VB95 V

Table 2–3 — VI-200, VI-J00 output voltage designators

Output

Voltage

<5 Vdc 10 – 40 A 5 – 20 A 10 – 30 A 5 – 10 A

≥5 Vdc 50 – 200 W 25 – 100 W 50 – 100 W 10 – 50 W

Table 2–4 — Output voltage vs. power level

Special output voltages from 1 – 95 V; consult factory.

T (TRIM). Provides fixed or variable adjustment of the
module output.

Trimming Down. Allows output voltage of the module to
be trimmed down, with a decrease in efficiency. Ripple as
a percent of output voltage goes up and input range
widens since input voltage dropout (loss of regulation)
moves down.

Trimming Up. Reverses the above effects.

Power Level Power Level

VI-200 VI-J00 MI-200 MI-J00

–S, +S (–SENSE, +SENSE). Provides for locating the point
of optimal voltage regulation external to the converter.

GATE OUT. The pulsed signal at the GATE OUT pin of a
regulating Driver module is used to synchronously drive
the GATE IN pin of a companion Booster module to effect
power sharing between the Driver and the Booster. Daisy­chaining additional Boosters (connecting GATE OUT of
one unit to GATE IN of a succeeding unit) leads to a
virtually unlimited power expansion capability.

Output OVP in VI-/MI-200 will trip if remote sense
compensates output voltage measured at output pins
above 110% of nominal. Discrete wire used for sense
must be tightly twisted pair. Do not exceed 0.25 V drop in
negative return; if the voltage drop exceeds 0.25 V in the
negative return path, the current limit setpoint will increase.
Connect +SENSE to +OUT and –SENSE to –OUT at the
module if remote sensing is not desired.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 3 of 98

Apps. Eng. 800 927.9474 800 735.6200

(Figure 7–4)

3. Module Do’s and Dont’s

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

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Design Guide & Applications Manual

ELECTRICAL CONSIDERATIONS
GATE IN AND GATE OUT PINS

Logic Disable. When power is applied to the input pins,
the GATE IN pin of a Driver can be pulled low with respect
to the –IN thus turning off the output while power is still
applied to the input. (Figure 7–1)

CAUTION: With offline applications –IN is not
earth ground.

In Logic Disable mode, the GATE IN pin should be driven
from either an “open collector” or electromechanical
switch that can sink 6 mA when on (GATE IN voltage less
than 0.65 V). If driven from an electromechanical switch
or relay, a 1 µF capacitor should be connected from GATE IN
to –IN to eliminate the effects of switch “bounce”. The 1 µF
capacitor may be required in all applications to provide a
“soft start” if the unit is disabled and enabled quickly. Do
not exceed a repetitive on / off rate of 1 Hz to the GATE
IN or input voltage pins.

High Power Arrays. The pulsed signal at the GATE OUT
pin of a regulating Driver module is used to synchronously
drive the GATE IN pin of a companion Booster module to
effect power sharing between the Driver and the Booster.

(Figure 7–5) Daisy-chaining additional Boosters (i.e.,

connecting GATE OUT to GATE IN of a succeeding unit)
leads to a virtually unlimited power expansion capability.
VI-/MI-200 series modules of the same family and power
level can be paralleled (i.e., Driver, VI-260-CU with
Booster, VI-B60-CU).

In general:

• Don’t drive the GATE IN pin from an “analog”
voltage source.

• Don’t leave GATE IN pins of Booster modules
unterminated.

• Don’t overload GATE OUT; limit load to a single Vicor
module GATE IN connection, or 1 kΩ, minimum, in
parallel with 100 pF, maximum.

• Don’t skimp on traces that interconnect module –IN
pins in high power arrays. GATE IN and GATE OUT
are referenced to –IN; heavy, properly laid out traces will
minimize parasitic impedances that could interfere with
proper operation.

• Do use a decoupling capacitor across each module’s
input (see Input Source Impedance that follows).

• Do use an EMI suppression capacitor from +/– input and
output pins to the baseplate.

• Do use a fuse on each module’s + input to prevent fire
in the event of module failure. See safety agency
conditions of acceptability for the latest information on
fusing. Please see the Vicor website
for Safety Approvals.

Input Source Impedance. The converter should be
connected to an input source that exhibits low AC
impedance. A small electrolytic capacitor should be

ounted close to the module’s input pins. (C3, Figure 3–1)

m
This will restore low AC impedance, while avoiding the

otential resonance associated with “high-Q” film

p
capacitors. The minimum value of the capacitor, in
microfarads, should be C (µF) = 400 ÷ Vin minimum.
Example: Vin, minimum, for a VI-260-CV is 200 V. The
minimum capacitance would be 400 ÷ 200 = 2 µF. For
applications involving long input lines or high inductance,
additional capacitance will be required.

The impedance of the source feeding the input of the
module directly affects both the stability and transient
response of the module. In general, the source impedance
should be lower than the input impedance of the module
by a factor of ten, from DC to 50 kHz.

To calculate the required source impedance, use the
following formula:

L

n

L

Z = 0.1(V

)2/ Pi

where: Z is required input impedance

VLL is the low line input voltage
Pin is the input power of the module

Filters, which precede the module, should be well damped
to prevent ringing when the input voltage is applied or
the load on the output of the module is abruptly changed.

Input Transients. Don’t exceed the transient input
voltage rating of the converter. Input Attenuator Modules
or surge suppressors in combination with appropriate
filtering, should be used in offline applications or in
applications where source transients may be induced by
load changes, blown fuses, etc. For applications where the
input voltage may go below low line it is recommended
that an undervoltage lockout circuit be used to pull GATE
IN low to disable the converter module. The undervoltage
lockout circuit should induce a delay of at least one
second before restarting the converter module. Longer
delays will be required if external capacitance is added at
the output to insure the internal soft-start is re-initialized.

NOTE: Do not allow the rate of change of the input
voltage to exceed 10 V/µs for any input voltage deviation.

The level of transient suppression required will depend on
the severity of the transients. A Zener diode, TRANSZORB™
or MOV will provide suppression of transients under 100 µs
and act as a voltage clipper for DC input transients. It may
be necessary to incorporate an LC filter for larger energy
transients. This LC filter will integrate the transient energy
while the Zener clips the peak voltages. The Q of this filter
should be kept low to avoid potential resonance problems.
See Section 14, Input Attenuator Module (IAM / MI-IAM)
for additional information on transient suppression.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 4 of 98

Apps. Eng. 800 927.9474 800 735.6200

Design Guide & Applications Manual

+OUT

+IN

–IN

–OUT

Zero Current

Switching
Converter

C1a

C1b

C2a

C2b

C3

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

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3. Module Do’s and Dont’s

Output OVP. The VI-/MI-200, with the exception of

I-/ MI-J00s, has an internal overvoltage protection circuit

V
that monitors the voltage across the output power pins. It
is designed to latch the converter off at 115 – 135% of
rated output voltage. It is not a crowbar circuit, and if a
module is trimmed above 110% of rated output voltage,
OVP may be activated. Do not backdrive the output of
the converter module to test the OVP circuit.

CAUTION:

When trimming up VI-/MI-J00 modules,
additional care should be taken as an improper
component selection could result in module failure.
Improper connection of the sense leads on VI-/MI-J00
modules can also result in an excessive overvoltage
condition and module failure.

Input Reverse Voltage Protection. The module may be
protected against reverse input voltages by the addition of
a diode in series with the positive input, or a reverse
shunt diode with a fuse in series with the positive input.
See Section 14, the Input Attenuator Module (IAM/MI-IAM)
provides input reverse voltage protection when used with
a current limiting device (fuse).

THERMAL / MECHANICAL CONSIDERATIONS

Baseplate. Operating temperature of the baseplate, as
measured at the center mounting slot on the –IN, –OUT
side, can not exceed rated maximum. ThermMate or
thermal compound should be used when mounting the
module baseplate to a chassis or heat sink. All six
mounting holes should be used. Number six (#6) machine
screws should be torqued to 5-7 in-lbs, and use of Belville
washers is recommended.

THERMAL AND VOLTAGE HAZARDS

Vicor component power products are intended to be used

ithin protective enclosures. Vicor DC-DC converters

w
work effectively at baseplate temperatures, which could
be harmful if contacted directly. Voltages and high
currents (energy hazard) present at the pins and circuitry
connected to them may pose a safety hazard if contacted
or if stray current paths develop. Systems with removable
circuit cards or covers which may expose the converter(s)
or circuitry connected to the converters, should have proper
guarding to avoid hazardous conditions.

EMC CONSIDERATIONS

All applications utilizing DC-DC converters must be properly
bypassed, even if no EMC standards need to be met. Bypass
IN and OUT pins to each module baseplate as shown in
Figure 3–1. Lead length should be as short as possible.
Recommended values vary depending on the front end, if
any, that is used with the modules, and are indicated on the
appropriate data sheet. In most applications, C1a – C1b is a
4,700 pF Y-capacitor (Vicor Part # 01000) carrying the
appropriate safety agency approval; C2a – C2b is a 4,700 pF
Y-capacitor (Vicor Part # 01000) or a 0.01 µF ceramic
capacitor rated at 500 V. In PCB mount applications, each of
these components is typically small enough to fit under the
module baseplate flange.

The module pins are intended for PCB mounting either by
wave soldering to a PCB or by insertion into one of the
recommended PCB socket solutions.

CAUTION: Use of discrete wires soldered directly
to the pins may cause intermittent or permanent
damage to the module; therefore, it is not
recommended as a reliable interconnection scheme
for production as a final released product. See

Section 21 for packaging options designed for

discrete wire connections (BusMod, MegaMod).

Figure 3–1 — IN and OUT pins bypassed to the module baseplate
and input cap for low AC impedance

In addition, modules that have been soldered into printed
circuit boards and have subsequently been removed
should not be reused.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 5 of 98

Apps. Eng. 800 927.9474 800 735.6200

3. Module Do’s and Dont’s

SAFETY CONSIDERATIONS

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

Shock Hazard. Agency compliance requires that the
baseplate be grounded.

Fusing. Internal fusing is not provided in Vicor DC-DC

onverters. To meet safety agency conditions, a fuse is

c
required. This fuse should be placed in the positive input
lead, not the negative input lead, as opening of the
negative input lead will cause the GATE IN and GATE OUT
to rise to the potential of the +IN lead, causing possible
damage to other modules or circuits that share common
GATE IN or GATE OUT connections.

Acceptable Fuse Types and Current Rating for the VI-200 and VI-J00 Family of Converters

Package Size Required Fuse Package Size Required Fuse

VI-27x-xx PC-Tron 2.5 A VI-J7x-xx PC-Tron 2.5 A
VI-26x-xx PC-Tron 3 A VI-J6x-xx PC-Tron 3 A

VI-25x-xx PC-Tron 5 A VI-J5x-xx PC-Tron 5 A

VI-2Tx-xx PC-Tron 5A VI-JTx-xx PC-Tron 5A

VI-24x-xx 6 A / 125 V VI-J4x-xx PC-Tron 5A

Safety agency conditions of acceptability require module
input fusing. The VI-x7x, VI-x6x and VI-x5x require the use
of a Buss PC-Tron fuse, or other DC-rated fuse. See below
for suggested fuse ratings.

The safety approvals section of the Vicor website should
always be checked for the latest fusing and conditions of
acceptability information for all DC-DC converters
including the MegaMod family.

VI-2Nx-xx 8A / 125 V VI-JNx-xx PC-Tron 5A

VI-23x-xx 8 A /125 V VI-J3x-xx PC-Tron 5A

VI-22x-xx 8 A / 60 V VI-J2x-xx PC-Tron 5A

VI-2Wx-xx 12 A / 50 V VI-JWx-xx 8 A / 60 V

VI-21x-xx 12 A / 32 V VI-J1x-xx 8 A / 60 V

VI-2Vx-xx 12 A / 32 V VI-J0x-xx 8 A / 60 V

VI-20x-xx 12 A / 32 V

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 6 of 98

Apps. Eng. 800 927.9474 800 735.6200

Design Guide & Applications Manual

2 V

V

out

I

c

I

fb

I

max

I

out

I

short circuit

V

out

I

short circuit

I

c

I

max

I

out

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

4. Overcurrent Protection

FOLDBACK CURRENT LIMITING

The VI-/MI-200 modules with output voltages of 5 V or

3.3 V incorporate foldback current limiting. (Figure 4–1) In
his mode, the output voltage remains constant up to the

t
current knee, (Ic), which is 5 – 25% greater than full-rated

urrent, (Imax). Beyond Ic, the output voltage falls along

c
the vertical line Ic– Ifb until approximately 2 V. At ≤2 V, the
voltage and current folds back to short circuit current
point (20 – 80% of Imax). Typically, modules will
automatically recover when overcurrent is removed.

When bench testing modules with foldback current limiting,
use a constant resistance load as opposed to a constant
current load. Some constant current loads have the ability
to pull full current at near zero volts. This may cause a
latchup condition. Also when performing a short circuit
test it is recommended to use a mercury wetted relay to
induce the output short as other methods may induce
switch bounce that could potentially damage the converter.

STRAIGHT LINE CURRENT LIMITING

The VI-/MI-200 modules with output voltages greater
than 5 V, 2 V (VI-/MI-200 only) and all

odules incorporate a straight-line type current limit.

m

VI-/MI-J00

(Figure 4–2) As output current is increased beyond Imax,

he output voltage remains constant and within its

t
specified limits up to a point, Ic, which is 5 – 25% greater
than rated current, (Imax). Beyond Ic, the output voltage
falls along the vertical line to Isc. Typically, modules will
automatically recover after overcurrent is removed.

Figure 4–1 — Foldback current limiting

Apps. Eng. 800 927.9474 800 735.6200

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 7 of 98

Figure 4–2 — Straight-line current limiting

5. Output Voltage Trimming

+OUT

+SENSE

–OUT

R

3

–
+

C1

Load

[

a]

F

or Vout < 3.3 V, R5 = 3.88 kΩ and internal reference = 0.97 V.

E

rror Amp

R

1 47 Ω Typ.

R4 27 Ω Typ.

R2

R

5 10 kΩ

[

a]

TRIM

R6

–SENSE

R8

R

7

2.5 V

[a]

R6

TRIM

–SENSE

–OUT

R7 10 kΩ POT

R5 10 kΩ

[a]

(internal)

V1

R8

I

R6

2.5 V

[a]

reference

(internal)

[a]

For Vout < 3.3 V, R5 = 3.88 kΩ and internal reference = 0.97 V.

+OUT

+SENSE

–SENSE

OVERVIEW

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

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Design Guide & Applications Manual

Specifications such as efficiency, ripple and input voltage
range are a function of output voltage settings. As the
output voltage is trimmed down, efficiency goes down;
ripple as a percent of Vout goes up and the input voltage
range widens since input voltage dropout (loss of regulation)
moves down. As the units are trimmed up, the reverse of
the above effects occurs.

All converters have a fixed current limit. The overvoltage
protection setpoint is also fixed; trimming the output
voltage does not alter its setting. As the output voltage is
trimmed down, the current limit setpoint remains constant.
Therefore, in terms of output power, if the unit is trimmed
down, available output power drops accordingly.

The output voltage of most Vicor converters can be
trimmed +10%, –50%. Certain modules have restricted
trim ranges. Consult the latest datasheet for details.

Do not attempt to trim the module output voltage more
than +10%, as overvoltage shut down may occur. Do not
exceed maximum rated output power when the module is
trimmed up.

CAUTION: When trimming up VI- / MI-J00 converter
modules, additional care should be taken as an
improper component selection could result in module
failure. Improper connection of the sense leads on
VI-/ MI-J00 converter modules can also result in an
excessive overvoltage condition and module failure.

Example 1. For trimming –10% to +10% with a standard
off-the-shelf 10 kΩ potentiometer (R7), values for resistors
R6 and R8 need to be calculated.

esistor R6 limits the trim down range. For a given

R
percentage, its value is independent of output voltage.
Refer to

Figure 5–1 — External resistive network for variable trimming

Table 5–1, for limiting resistor values.

TRIMMING DOWN –10%

A 10% drop of the 2.5 V reference at the TRIM pin is
needed to effect a 10% drop in the output voltage.
(Figure 5–2)

The following procedures describe methods for output
voltage adjustment (–10 to +10% of nominal) of the
VI-/MI-200, VI-/MI-J00, ComPAC/MI-ComPAC, FlatPAC
and MegaMod / MI-MegaMod Families.

Modules with nominal 3.3 V outputs and above have
the 2.5 V precision reference and 10 k internal resistor.
For trim resistor calculations on modules with 2.0 V
outputs use 0.97 V in place of the 2.5 V reference
and substitute 3.88 kΩ for the internal 10 kΩ resistor.

Figure 5–2 — Circuit diagram “Trim Down”

Resistors are 0.25 W. When trimming down any module,
always maintain a minimum preload of at least 1% of
rated output power and in some cases up to 10% may be
required. For more specific information on trimming down

Therefore:
a specific module, please consult Vicor’s Applications
Engineering Department at [phone].

RESISTIVE ADJUSTMENT PROCEDURE

Since IR5 = IR6 = 25 µA:

To achieve a variable trim range, an external resistor
network must be added. (Figure 5–1)

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 8 of 98

Apps. Eng. 800 927.9474 800 735.6200

This value will limit the trim down range to –10% of

nominal output voltage.

V1 = 2.5 V – 10% = 2.25 V

(2.5 V – 2.25 V)

IR5 =

R6 =

10 kΩ

2.25 V
25 µA

= 25 µA

= 90 kΩ

Design Guide & Applications Manual

I

V2

R6 90 kΩ

TRIM

+ SENSE

–

SENSE

– OUT

R

5 10 kΩ

[a]

(internal)

V

1

R

8

R

8

R

7 10 kΩ POT

500 µA

25 µA

2.5 V

[a]

r

eference

(internal)

+ OUT

[a]

For Vout < 3.3 V, R5 = 3.88 kΩ and inter nal reference = 0.97 V.

TRIM

+ OUT

+ SENSE

– SENSE

– OUT

Rd

Ru

Trim Resistor for UP
Programming

Trim Resistor for DOWN
Programming

or

2.5 V

[a]

reference

(internal)

R5 10 kΩ

[a]

(internal)

[a]

For Vout < 3.3 V, R5 = 3.88 kΩ and inter nal reference = 0.97 V.

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

5. Output Voltage Trimming

TRIMMING UP +10%

To trim 10% above the nominal output voltage, the
following calculations are needed to determine the value
of R8. This calculation is dependent on the output voltage
of the module. A 12 V output will be used as an example.
(Figure 5–3)

It is necessary for the voltage at the TRIM pin to be 10%
greater than the 2.5 V reference. This offset will cause the
error amplifier to adjust the output voltage up 10% to 13.2 V.

Figure 5–3 — Circuit diagram “Trim Up”

FIXED TRIM

Converters can be trimmed up or down with the addition
of one external resistor, either Ru for programming up or
Rd for programming down. (Figure 5–4)

xample 2. Fixed Trim Up (12 V to 12.6 V).

E

To determine Ru, the following calculation must be made:

2.5 V + 5% = 2.625 V

5

= VT

RIM

R

V

– Vr

ef

VR5= 2.625 – 2.5 = 0.125 V

Knowing this voltage, the current through R5 can be found:

IR5 =

VR5

R5 10 kΩ

=

0.125
= 12.5 µA

VRu = 12.6 V – 2.625 V = 9.975 V

9.975

Ru =

12.5 µA

= 798 kΩ

V1 = 2.5 V + 10% = 2.75 V

(2.75 V – 2.5 V)

IR5 =

10 kΩ

= 25 µA

Since IR5 = IR6 ,
the voltage drop across R6 = (90 kΩ) (25 µA) = 2.25 V.

Figure 5–4 — Fixed trimming

Therefore, V2 = 2.75 V + 2.25 V = 5 V. The current
through R7 (10 kΩ pot) is:

IR7 =

V2

R7 10 k

5

=

= 500 µA

Using Kirchoff’s current law:

R8 = IR7 + IR6 = 525 µA

I

Thus, knowing the current and voltage, R8 can be
determined:

VR8 = (Vout + 10%) – V2 = 13.2 V – 5 V = 8.2 V

R8 =

(8.2 V)
525 µA

= 15.6 kΩ

Connect Ru from the TRIM pin to the +SENSE. Be sure to
connect the resistor to the +SENSE, not the +OUT, or
drops in the positive output lead as a function of load will
cause apparent load regulation problems.

Example 3. –25% Fixed Trim Down (24 V to 18 V).
The trim down methodology is identical to that used in
Example 2, except that it is utilized to trim the output of a
24 V module down 25% to 18 V. The voltage on the
TRIM pin must be reduced 25% from its nominal setting
of 2.5 V. This is accomplished by adding a resistor from
the TRIM pin to –SENSE.

2.5 V – 25% = 1.875 V
This resistor configuration allows a 12 V output module
to be trimmed up to 13.2 V and down to 10.8 V. Follow
this procedure to determine resistor values for other
output voltages.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 9 of 98

Apps. Eng. 800 927.9474 800 735.6200

VR5 = Vbandgap – VTRIM

= 2.5 V – 1.875 V = 0.625 V

5. Output Voltage Trimming

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

Knowing this voltage, the current through R5 can be found:

IR5 =

VR

R5 10 kΩ

=

0.625
= 62.5 µA

5

The voltage across the resistor, Rd, and the current

lowing through it are known:

f

Rd =

(2.5 V – 0.625 V)

= 30 kΩ

62.5 µA

Connect Rd (Figure 5–4) from the TRIM pin to the –SENSE
of the module. Be sure to connect the resistor to the
–SENSE, not the –OUT, or drops in the negative output
lead as a function of load will cause apparent load
regulation problems.

Values for Trim Down by Percentage

Percent Resistance

–5 % 190 kΩ
–10 % 90 kΩ
–15 % 56.7 kΩ
–20 % 40 kΩ
–25 % 30 kΩ
–30 % 23.3 kΩ
–35 % 18.6 kΩ
–40 % 15 kΩ
–45 % 12.2 kΩ
–50 % 10 kΩ

Table 5–1 — Values for trim down by percentage (Refer to product
data sheet for allowable trim ranges at

vicorpower.com)

Fixed Trim Down

Vnom V (Desired) Trim Resistor

5V 4.5 V 90.9 kΩ

3.3 V 19.6 kΩ

2.5 V 10.0 kΩ
15 V 13.8 V 115 kΩ
24 V 20 V 49.9 kΩ
48 V 40 V 49.9 kΩ

36 V 30.1 kΩ

Table 5–2a — Values for fixed trim down by voltage

[a]

DYNAMIC ADJUSTMENT PROCEDURE

Output voltage can also be dynamically programmed by
driving the TRIM pin from a voltage or current source;
programmable power supplies and power amplifier
applications can be addressed in this way. For dynamic
programming, drive the TRIM pin from a source referenced
to the negative sense lead, and keep the drive voltage in
the range of 1.25 – 2.75 V. Applying 1.25 – 2.5 V on the
TRIM pin corresponds to 50 – 100% of nominal output
voltage. For example, an application requires a +10, 0%
(nominal), and a –15% output voltage adjustment for a 48 V
output converter. Referring to the table below, the voltage
that should be applied to the trim pin would be as follows:

VT

RIM

VO

UT

Change from nominal

2.125 40.8 –15%

2.5 48 0

2.75 52.8 +10%

The actual voltage range is further restricted by the
allowable trim range of the converter. Voltages in excess
of 2.75 V (+10% over nominal) may cause overvoltage
protection to be activated. For applications where the
module will be programmed on a continuous basis the
slew rate should be limited to 30 Hz sinusoidal.

TRIMMING ON THE WEB (VICORPOWER.COM)

Trim values are calculated automatically. Design
Calculators are available on Vicor’s website in the
PowerBenchTMsection at

www.vicorpower.com/powerbench.

Resistor values can be easily determined for fixed trim up,
fixed trim down and for variable trimming applications.

In addition to trimming information, the website also
includes design tips, applications circuits, EMC
suggestions, thermal design guidelines and PDF data
sheets for all available Vicor products.

Fixed Trim Up

Vnom V (Desired) Trim Resistor

5V 5.2 V 261 kΩ

5.5 V 110 kΩ
12 V 12.5 V 953 kΩ

13.2 V 422 kΩ

15 V 15.5 V 1.62 MΩ

16.5 V 562 kΩ
24 V 25 V 2.24 MΩ
48 V 50 V 4.74 MΩ

Table 5–2b — Values for fixed trim up by voltage

[a]

Values listed in the tables are the closest standard 1% resistor values.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 10 of 98

Apps. Eng. 800 927.9474 800 735.6200

[a]

Design Guide & Applications Manual

+IN

–IN

GATE
OUT

GATE
IN

+IN

–IN

GATE
OUT

GATE
IN

Vicor

DC-DC Converter

F1

C1

Z1

C3

SW1

F2

DISABLE

D2

Z2 C2

D1

Vicor

DC-DC Converter

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

OVERVIEW

6. Multiple GATE IN Connections

A number of GATE IN pins may be connected for remote
shut down and logic disable. (Figure 6-1) Diodes D1 and
D2 provide isolation and prevent multiple failures if the
GATE IN of a module becomes shorted to the +IN. The
Zener diodes Z1, Z2 and capacitors C1, C2 attenuate
transient voltage spikes caused by differential inductance
in the negative lead. Capacitors C1 and C2 will also

C1, C2, C3 = 1 µF
Z1, Z2 = 15 V (1N5245B)
D1, D2 = Small signal diode (1N4148)

[a]

For bus voltages greater than 75 V,
a 1N4006 diode should be used.

[a]

lengthen turn-on time. SW1 is a mechanical or solid state
switch that is used to disable both Driver modules. C3 is
used to minimize the effects of “switch bounce” associated
with mechanical devices.

NOTE: GATE IN voltage needs to be <0.65 V
referenced to –IN to ensure modules are disabled.

NOTE:

The –IN to –IN input lead should be kept as short as possible to minimize differential inductance.

Heavy lines indicate power connections. Use suitably sized conductors.

Opto-couplers or relays should be used to isolate GATE IN connections, if the converters are on
separate boards or the negative input lead’s impedance is high.

Figure 6–1 — Protection for multiple GATE IN connections

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 11 of 98

Apps. Eng. 800 927.9474 800 735.6200

–OUT

–

S

+S

+OUT

+IN

GAT E
IN

G

AT E

OUT
–IN

Z

ero Current

Switching

Converter

Driver

+
–

1

6

TLP798G

Agilent 6N139

Load

2

5

TRIM

1µF

7. Application Circuits / Converter Array Design Considerations

–OUT

–S

TRIM

+S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

Zero Current

Switching

Converter

Driver

+
–

Load

+
–

–OUT

–

S

TRIM

+

S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

Z

ero Current

S

witching

C

onverter

D

river

+
–

L

oad

–OUT

–S

TRIM

+S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

Zero Current

Switching
Converter

Driver

+
–

Load

• • •• • •

• • •• • •

• • •• • •

• • •• • •

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

Logic Disable. (Figure 7–1) The GATE IN pin of the
module may be used to turn the module on or off. When
GATE IN is pulled low (<0.65 V @ 6 mA, referenced to

Vin), the module is turned off. When GATE IN is floating

–
(open collector), the module is turned on. The open circuit

oltage of the GATE IN pin is less than 10 V. This applies

v
to VI-/ MI-200, VI-/MI-J00 and MegaMod / MI-MegaMod
Family modules.

Output Voltage Programming. (Figure 7–2) Consult
Vicor’s Applications Engineering Department before
attempting large signal applications at high repetition
rates due to ripple current considerations with the internal
output capacitors. This applies to VI-/ MI-200, VI-/MI-J00,
ComPAC /MI-ComPAC, FlatPAC and MegaMod/
MI-MegaMod Family modules.

Vout =

Vtrim x Vnom

2.5

Negative Inputs (with positive ground). (Figure 7–3)
Vicor modules have isolated inputs and outputs making
negative input configurations easy. Fusing should always

e placed in the positive lead.

b

Remote Sensing. (Figure 7–4) Output voltage between
+OUT and –OUT must be maintained below 110% of
nominal. Do not exceed 0.25 V drop in negative return as
the current limit setpoint is moved out proportionately.
The sense should be closed at the module if remote
sensing is not desired. Applies to VI-/ MI-200, VI-/ MI-J00,
ComPAC /MI-ComPAC, FlatPAC and MegaMod/
MI-MegaMod Family modules. Excessively long sense leads
and / or excessive external capacitance at the load may
result in module instability. Please consult Vicor
Applications Engineering for compensation methods.

Figure 7–1 — Logic disable

Figure 7–2 — Output voltage programming

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 12 of 98

Apps. Eng. 800 927.9474 800 735.6200

Figure 7–3 — Negative inputs (with positive ground)

Figure 7–4 — Remote sensing

Design Guide & Applications Manual

–OUT

–S

T

RIM

+S

+OUT

+IN

GATE
IN

GATE
O

UT

–IN

Zero Current

S

witching

C

onverter

#1

Driver

VI-2xx-xx

+
–

–OUT

–S

TRIM

+S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

Zero Current

Switching
Converter

#n

Booster

VI-Bxx-xx

Load

–OUT

-S

TRIM

+S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

Zero Current

Switching
Converter

Driver

+
–

Load

V Control

0.1 V/A

1K

OP

AMP

–

+

1K

1K

0.05 Ω

1K

0.01

I

10 µF

–OUT

–S

TRIM

+S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

Zero Current

Switching

Converter

Driver

+
–

Load requiring
positive output

–OUT

–S

T

RIM

+S

+OUT

+

IN

GATE
IN

GATE
OUT

–IN

Z

ero Current
S

witching

C

onverter
Driver

+
–

Load requiring
negative output

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

7. Application Circuits / Converter Array Design Considerations

Parallel Boost. (Figure 7–5) U.S. Patent #4,648,020 —
other patents pending. To retain accurate power sharing
between a Driver and (n) number of Boosters, provide

dequate input and output power bussing. This applies to

a
VI-/MI-200 and MegaMod / MI-MegaMod Family

odules. See

m

odule Do’s and Don’tsfor recommended

M

external components. (Section 3)

Programmable Current Source. (Figure 7–6) Module
output voltage should not exceed the rated voltage of the
operational amplifier. This applies to VI-/ MI-200,
VI-/MI-J00, ComPAC/ MI-ComPAC, FlatPAC and

MegaMod/MI-MegaMod Family modules.

: When using a VI-J00 module, the TRIM pin

NOTE
voltage should be clamped to 2.75 V to avoid
damage to the module. This corresponds to the

aximum trim up voltage. This circuit or functional

m
equivalent must be used when charging batteries.

o not exceed the nominal current ratings of the

D
converter. Example,

Pout

Vnominal

Dual Output Voltages. (Figure 7–7) Vicor modules have
isolated outputs so they can easily be referenced to a
common node creating positive and / or negative rails.

Figure 7–5 — Parallel boost. U.S. Patent #4,648,020 — other

Figure 7–7 — Dual output voltages

patents pending.

Figure 7–6 — Programmable current source

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 13 of 98

Apps. Eng. 800 927.9474 800 735.6200

INPUT

LOAD

+S

TRIM

–S

–OUT

+IN
GATE

IN
GATE

OUT
–IN

+S

TRIM

–S

–OUT

+IN
GATE

IN
GATE

OUT
–IN

+S

TRIM

–S

–OUT

+IN
GATE

IN
GATE

OUT
–IN

+

–

Zero-Current-

Switching

Driver

VI-2xx-xx

Zero-Current-

Switching

Booster

VI-Bxx-xx

Zero-Current-

Switching

Booster

VI-Bxx-xx

+OUT

+OUT

+OUT

8. Using Boosters and Parallel Arrays

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

OVERVIEW

The VI-/MI-200 Family of DC-DC converters are available
as Driver or Booster modules. The Driver can be used as a
stand alone module, or in multi-kilowatt arrays by adding
parallel Boosters. Booster modules do not contain
feedback or control circuitry, so it is necessary to connect
the Booster GATE IN pin to the preceding Driver or
Booster GATE OUT, to synchronize operation. Drivers and
Boosters have identical power trains, although Drivers
close the voltage loop internally while Boosters do not.

The concept behind Driver / Booster operation is that two
or more ZCS power trains driven at the same frequency
will inherently load-share if their inputs and outputs are
tied together. Slaved modules require only one connection
between units when their outputs are connected
together; no trimming, adjustments or external
components are required to achieve load sharing. The
load sharing is dynamic and typically within 5%.

For additional information, refer to Electrical Considerations
– High Power Arrays in the Module Do’s and Don’ts.
(Section 3)

IMPORTANT: It is important to remember that when
using Boosters, the input voltage, output voltage and
output power of the Boosters must be the same as
the Driver.

Whenever power supplies or converters are operated in a
parallel configuration—for higher output power, fault
tolerance, or both—current sharing is an important

consideration. Most current-sharing schemes employed
with power converters involve analog approaches. One
analog method artificially increases the output impedance

f the converter modules, while another actually senses

o
the output current of each module and forces all of the

urrents to be equal by feedback control.

c

Synchronous current sharing offers an alternative to
analog techniques. In a synchronous scheme, there is no
need for a current-sensing or current-measuring device on
each module. Nor is there a need to artificially increase
output impedance, which compromises load regulation.

There are advantages and disadvantages associated with
each approach to current sharing. In choosing the best
approach for a given application, designers should be
aware of the tradeoffs as well as tips for implementing a
successful design.

Most paralleled power components, such as transistors,
rectifiers, power conversion modules, and offline power
supplies, will not inherently share the load. With power
converters, one or more of the converters will try to
assume a disproportionate or excessive fraction of the
load unless forced current-sharing control is designed into
the system.

One converter, typically the one with the highest output
voltage, may deliver current up to its current limit setting,
which is beyond its rated maximum. Then, the voltage will
drop to the point where another converter in the array—
the one with the next highest voltage—will begin to
deliver current. All of the converters in an array may

Figure 8–1 — Parallel array

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 14 of 98

Apps. Eng. 800 927.9474 800 735.6200

Design Guide & Applications Manual

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

8. Using Boosters and Parallel Arrays

deliver some current, but the load will be shared unequally.
With built-in current limiting, one or more of the converters
will deliver current up to the current limit (generally 15 or

0% above the module’s rated maximum), while other

2
converters in the array supply just a fraction of load.

Consider a situation where one module in a two-module
array is providing all of the load. If it fails, the load on the
second module must go from no load to full load. During
that time, the output voltage is likely to droop temporarily.
This could result in system problems, including shutdown
or reset.

On the other hand, if both modules were sharing the load
and one failed, the surviving module would experience a
much less severe transient (one-half to full load). Also, the
output voltage would be likely to experience no more
than a slight momentary droop. The dynamic response
characteristic of all forward converters, resonant or pulse­width modulated, is degraded when the load is stepped
from zero (no load) where the output inductor current is
discontinuous.

In the same two-module array example, the module
carrying all of the load also is generating all of the heat.
That results in a much lower mean time between failure
for that module. An often-quoted rule of thumb says that
for each 10°C increase in operating temperature, average
component life is cut in half.

In a current-sharing system, the converters or supplies all
run at the same temperature. This temperature is lower
than that of the hot-running (heavily loaded) modules in
a system without current sharing. Furthermore, same­temperature operation means that all of the modules in
a current-sharing arrangement age equally.

Current sharing, then, is important because it improves
system performance. It optimizes transient and dynamic
response and minimizes thermal problems, which improves
reliability and helps extend the lifetimes of all of the
modules in an array. Current sharing is an essential
ingredient in most systems that use multiple power supplies
or converters to achieve higher output power or fault
tolerance.

When parallel supplies or converters are used to increase
power, current sharing is achieved through a number of
approaches. One scheme simply adds resistance in series
with the load. A more practical variant of that is the
“droop-share” method, which actively causes the output
voltage to drop in response to increasing load.
Nevertheless, the two most commonly used approaches
to paralleling converters for power expansion are Driver /
Booster arrays and analog current-sharing control. They
appear to be similar, but the implementation of each is
quite different.

Driver / Booster arrays usually contain one intelligent
module or Driver, and one or more power-train-only
modules or Boosters. Analog current-sharing control

nvolves paralleling two or more identical modules, each

i
containing intelligence.

One of the common methods of forcing load sharing in
an array of parallel converters is to sense the output
current of each converter and compare it to the average
current. Then, the output of a given converter is adjusted
so that its contribution is equal to the average. This is
usually accomplished by current-sense resistors in series
with the load, a sensing amplifier for each converter
module, and a summing amplifier. Load sharing is
accomplished by actively trimming the output voltage
using TRIM or SENSE pins.

Occasionally, a designer is tempted to avoid the expense
of a current-sense resistor by using the IR drops in the
wire as a means of sensing the current. Unfortunately,
there are a number of negative issues associated with
that idea. First of all, there’s the temperature coefficient
of copper. As the wire heats up, its resistance increases,
negating its value as a stable current-sensing device.
Second, there are oxidation and corrosion issues, which
also cause parametric changes. Consequently, a high­precision current-sensing device, such as a precision
resistor, is a must.

The resistor values typically range from a few milliohms
up to about 100 mΩ, depending on the power level or
current range of operation. Selecting the right value
requires a tradeoff between power dissipation and
sensitivity (signal-to-noise ratio or noise immunity). The
larger the resistor value, the better the noise immunity—
and the greater the power dissipation.

Determining the size of the resistor needed to generate a
signal above the noise can be a bit tricky. Another
potential pitfall with this (or, for that matter, any other)
approach is the need for good electrical and mechanical
design and layout. This requires adequate trace widths,
minimized trace lengths, and decoupling to reduce noise.
An experienced designer should have no difficulty with
this, but it is an area rich with opportunities for error.

The droop-share method artificially increases the output
impedance to force the currents to be equal.
It’s accomplished by injecting an error signal into the
control loop of the converter, causing the output voltage
to vary as a function of load current. As load current
increases, output voltage decreases. All of the modules
will deliver approximately the same current because they
are all being summed into one node.

If one supply is delivering more current than another
supply, its output voltage will be slightly forced down so

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 15 of 98

Apps. Eng. 800 927.9474 800 735.6200

–OUT

–S

TRIM

+S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

–OUT

–S

TRIM

+S

+OUT

+IN

GATE
IN

GATE
OUT

–IN

Return

Zero Current

Switching

Converter

#1

Driver

Zero Current

Switching
Converter

#n

Driver

+V

IN

+V

OUT

–V

IN

8. Using Boosters and Parallel Arrays

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

that it will be delivering equal current for an equal voltage
at the summing node. A simple implementation of the
droop-share scheme uses the voltage dropped across an

Ring diode, which is proportional to current, to adjust

O
the output voltage of the associated converter. (Figure 8–2)

Droop share has advantages and disadvantages. One of
the advantages is that it can work with any topology. It’s
also fairly simple and inexpensive to implement. Though, a
major drawback is that it requires that the current be
sensed. A current-sensing device is needed in each of the
converters or power supplies. Additionally, a small penalty
is paid in load regulation, though in many applications this
isn’t an issue.

In general, mixing and matching converters isn’t
recommended—especially those with incompatible
current-sharing schemes. The droop-share method,
however, is more forgiving in this regard than any of the
other techniques. With a little external circuitry, current
sharing can be achieved using arrays constructed from
different converter models or even from different suppliers.

Most systems can employ the Driver / Booster (or master /
slave) array for increased power. (Figure 8–3) The Driver is
used to set and control output voltage, while Booster
modules, as slaves to the master, are used to extend
output power to meet system requirements.

Driver / Booster arrays of quasi-resonant converters with
identical power trains inherently current share because the
per-pulse energy of each converter is the same. If the
inputs and outputs are tied together and the units operate
at the same frequency, all modules will deliver equal
current (within component tolerances).

The single intelligent module in the array determines the
transient response, which does not change as modules
are added. Slaved modules require only one connection

etween units when their outputs are connected. No

b
trimming, adjustments, or external components are

equired to achieve load sharing. The load sharing is

r
dynamic and usually guaranteed within 5%. It’s important
to remember that when using Boosters, the input and
output voltage and output power specifications of the
Boosters must be the same as the Driver.

Driver / Booster arrays have two advantages. They have
only a single control loop, so there are no loop-within-a­loop stability issues. And, they have excellent transient
response. However, this arrangement isn’t fault tolerant.
If the Driver module fails, the array won’t maintain its
output voltage.

Analog current-sharing control involves paralleling two or
more identical modules, each containing intelligence. The
circuit actively adjusts the output voltage of each supply
so the multiple supplies deliver equal currents. This method,
though, has a number of disadvantages. Each converter in
the array has its own voltage regulation loop, and each
requires a current-sensing device and current-control loop.

Analog current-sharing control does support a level of
redundancy. But it’s susceptible to single-point failures
within the current-sharing bus that at best can defeat
current sharing, and at worst can destroy every module in
the array. The major reason for this is the single-wire
galvanic connection between modules.

Current sharing is an essential element in fault-tolerant
arrays. Yet regardless of the approach, there is an inherent

Figure 8–2 — Droop-share current sharing artificially increases converter output impedance to force the currents to be equal. Diodes on the
output of each converter provide current sensing and fault protection.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 16 of 98

Apps. Eng. 800 927.9474 800 735.6200

Design Guide & Applications Manual

INPUT

LOAD

+ Sense

T

rim

–Sense

GATE
IN

–

IN

Zero-Current-

Switching Driver

+

OUT

GATE
OUT

+IN

–OUT

+Sense

Trim

–Sense

–IN

Zero-Current-

Switching Booster

+OUT

+IN

–OUT

+Sense

Trim

–Sense

–IN

Zero-Current-

Switching Booster

+OUT

+IN

–OUT

+V

I

N

-V
IN

GATE
IN

GATE
OUT

GATE
IN

GATE
OUT

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

8. Using Boosters and Parallel Arrays

cost incurred by the addition of at least one redundant

onverter or supply.

c

ncidentally, most applications today that require fault

I
tolerance or redundancy also require Hot-Swap capability
to ensure continuous system operation. Hot-swappable
cards must be designed so the operator won’t come in
contact with dangerous potentials and currents.

It’s also essential that when a module fails, the failure is
detected and identified by an alarm or notice to provide
service. A Hot-Swap system must ensure that during
swap-out, there is minimal disturbance of the power bus.
Specifically, the affected voltage bus must not drop
enough to cause errors in the system, either on the input
bus or the output bus.

A power-supply failure can cripple an entire system, so the
addition of a redundant converter or supply is often
justified by the need to keep the system operating.
Adding an extra module (N+1) to a group of paralleled
modules will significantly increase reliability with only a
modest increase in cost.

The implementation of redundant converters is
determined in part by the available space and cost
requirements. For example, two 200 W full-size modules

could be used to provide a 400 W output with an

dditional 200 W module for 2+1 redundancy (a total of

a
600 W in a volume of about 16.5 in

3

).

Alternatively, four 100 W half-size modules might be used
with a fifth 100 W module to provide 4+1 redundancy (a
total of 500 W and 14 in3). Although the second solution
uses less space, it increases the accumulated failure rate
because it employs more converters, more ORing diodes,
more monitoring circuitry, and more assembly.

ORing diodes may be inserted in series with the output
of each module in an N+1 array to provide output fault
tolerance. (Figure 8–2) They’re important in a redundant
power system to maintain fault isolation. Without them,
a short-circuit failure in the output of one converter could
bring down the entire array.

But ORing diodes add losses to the power system,
reducing overall efficiency and decreasing reliability. To
ameliorate the negative effect on efficiency, ORing diodes
should run hot, thereby reducing forward voltage drop
and increasing efficiency. Reverse leakage current will be
an issue only if the output of a converter shorts and the
diode is reverse biased. This is an important consideration
with regard to operating temperature.

Figure 8–3 — Most converters can use the Driver / Booster array to increase output power. Driver / Booster arrays usually contain one
intelligent module or Driver, and one or more power-train-only modules or Boosters.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 17 of 98

Apps. Eng. 800 927.9474 800 735.6200

+IN

GATE
IN

GATE
OUT

–IN

+OUT

+S

TRIM

–S

–OUT

C2

C1

C2

C3

C3

C1 = 100 µF
C2 = 4,700 pF
C3 = 0.01 µF

Conditions:

Light Load = 3 A
Nominal Line = 48 V Nominal Load = 15 A
Full Load = 30 A

9. EMC Considerations

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

CONDUCTED NOISE

Conducted noise is the AC current flowing between the
source voltage and the power supply. It includes both
common-mode and differential-mode noise. Vicor zero-

urrent-switching converters are 20 – 40 dB lower in

c
conducted noise than a traditional board-mounted PWM
converter; however, if a specific EMC specification such as
FCC or VDE must be met, additional filtering may be required.

Since the noise generated is ten to a hundred times lower
than fixed frequency converters, an existing filter should
provide equal or better performance when the conditions
in the Module Do’s and Don’ts section are followed.
(Section 3)

In the event the system does not contain an existing filter,
the following will provide valuable information relative to
the attainment of system conducted noise objectives.
System requirements, such as Tempest (military) or UL544/
EN60601 (medical), require a somewhat different approach.
Medical requirements vary as a function of the application
and country — please contact Vicor Applications
Engineering for additional details.

Common-Mode Noise with No Additional Filtering.
Common mode conducted noise current is the
unidirectional (in phase) component in both the +IN and
–IN pins to the module. This current circulates from the
converter via the power input leads to the DC source and
returns to the converter via the grounded baseplate or
output lead connections. This represents a potentially
large loop cross-sectional area which, if not effectively
controlled, can generate magnetic fields. Common-mode
noise is a function of the dv/dt across the main switch in
the converter and the effective input to baseplate and
input to output capacitance of the converter.

The most effective means to reduce common-mode current
is to bypass both input leads to the baseplate with
Y-capacitors (C2), keeping the leads short to reduce
parasitic inductance. Additionally, a common-mode choke
(L1) is usually required to meet FCC/ VDE A or B. (Figure
9–2)

NOTE:

Acoustic Noise. Audible noise may be emitted
from the module under no load, light load, or
dynamic loading conditions. This is considered
normal operation of the module.

Typical Vicor Module

48 V Input, 5 V Output (VI-230-CV)

Conducted Noise vs. Load

3 Amp Load 15 Amp Load 30 Amp Load

Figure 9–1 — Conducted input noise, no additional filtering

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 18 of 98

Apps. Eng. 800 927.9474 800 735.6200

Design Guide & Applications Manual

+IN

–IN

+OUT

–

OUT

C1 = 2.2 µF
C2 = 100 µF
C3 = Internal
C4 = Internal
L1 = 3 mH

Conditions:

L

ight Load = 3 A
Nominal Load = 15 A
Full Load = 30 A

C1

L1

C

2

C3

C3

C4

C4

Nominal Line = 48 V

C

M

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

9. EMC Considerations

Common-Mode Noise with Common-Mode Choke.

There are no special precautions that must be exercised in
the design of input filters for Vicor converters. In fact, if

he system contains an EMC filter designed for typical

t
fixed frequency converters, it should be sufficient as is

although not optimal in terms of size), as zero-current-

(
switching converters inherently generate significantly less
conducted noise.

The plots in Figure 9–2 are representative of fixed
frequency converters with input filtering.

Typical Fixed Frequency Converter (PWM)

48 V Input, 5 V Output

: In most cases, a fixed frequency converter

NOTE
generates more input conducted noise with a filter
than Vicor’s zero-current-switching converter without

filter. Also note that fixed frequency converters

a
using a construction technique involving control

ircuitry on the same metal plate as power processing

c
components will generate significantly more input
noise than shown.

Conducted Noise vs. Load

3 Amp Load 15 Amp Load 30 Amp Load

Figure 9–2 — Conducted input noise, typical fixed frequency converter with filter

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 19 of 98

Apps. Eng. 800 927.9474 800 735.6200

9. EMC Considerations

C

4

C1 = 100 µF

C2

a –

C

2

b

= 4,700 pF (Vicor Part # 01000)

C3

a

–

C3

b

= 0.01 µF

(Vicor Part # 04872)

C4 = 2.2

µF

L1 = 3,000

µH

(Vicor Part # 31742)

Conditions

L

ight Load = 3 A

Nominal Load = 15 A

Full Load = 30 A

+IN

GATE
I

N

GATE
OUT

–IN

+

OUT

+

S

T

RIM

–

S

–OUT

C

2

a

C

1

C

2

b

C

3

b

C

3

a

L1

CM

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Typical Vicor Module (VI-230-CV)

48 V Input, 5 V Output

Three common-mode chokes are offered as standard accessories.

Part Inductance Maximum Resistance

Number Each Winding DC Current Each Winding

31743 1,000 µH 12 Amperes 6.5 mΩ
31742 3,000 µH 7 Amperes 18 mΩ
31943 2,163 µH 1 Ampere 42 mΩ

: Common-mode filters may be common to one or

NOTE
more modules, but only one
interconnected via GATE IN’s or, GATE OUT to GATE IN. As
an example, Driver / Booster arrays or Drivers with GATE IN’s
tied together to provide a common disable function.

Conducted Noise vs. Load

Design Guide & Applications Manual

should be used with modules

3 Amp Load 15 Amp Load 30 Amp Load

Figure 9–3 — Conducted input noise, with common-mode choke

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 20 of 98

Apps. Eng. 800 927.9474 800 735.6200

Design Guide & Applications Manual

+IN

GATE
IN
G

ATE
OUT
–IN

+OUT

+S

T

–S

–OUT

Load 1

Load 2

L

2

C4

L1

C1

a

C

2

a

C2

d

C2

c

C2

b

C3

a

C3

b

C3

c

C3

d

C1

b

+IN

GATE
IN
GATE
OUT
–IN

+OUT

+S

T

–S

–OUT

C1a – C1b = 47 µF
C2a – C2d = 4,700 pF (Vicor Part # 01000)
C3a – C3d = 0.01 µF (Vicor Part # 04872)
C4 = 2.2 µF
L1 = 3,000 µH (Vicor Part # 31742)
L2 = 20 µH

C

onditions

Light Load = 3 A
Nominal Load = 15 A
Full Load = 30 A

CM

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

9. EMC Considerations

Differential and Common-Mode Filter with More
than One Module. No special precautions are needed

when using two or more modules. The filter required will

ave the same characteristics as a single module filter,

h

Differential and Common-Mode Filter with More than One Module

48 V Inputs, 5 V Outputs (Two Vicor VI-230-CV Modules)

however the wire size on the magnetics will need to
reflect the increased input current. Shown below is the
input conducted noise for two modules sharing a

ommon input source.

c

Three common-mode chokes are offered as standard accessories.

Part Inductance Maximum Resistance

Number Each Winding DC Current Each Winding

31743 1,000 µH 12 Amperes 6.5 mΩ
31742 3,000 µH 7 Amperes 18 mΩ
31943 2,163 µH 1 Ampere 42 mΩ

: Common-mode filters may be common to one or

NOTE
more modules, but only one should be used with modules
interconnected via GATE IN’s or, GATE OUT to GATE IN. As
an example, Driver / Booster arrays or Drivers with GATE IN’s
tied together to provide a common disable function.

Conducted Noise vs. Load

3 Amp / 3 Amp Load

15 Amp / 15 Amp Load

Figure 9–4 — Conducted noise, multiple zero-current-switching converters

3 Amp / 6 Amp Load

3 Amp / 30 Amp Load

15 Amp / 30 Amp Load 30 Amp / 30 Amp Load

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 21 of 98

Apps. Eng. 800 927.9474 800 735.6200

9. EMC Considerations

C2

a

C

1

C2

b

C3

b

C3

a

L1

C

4

L2

C1 = 100 µF

C 2a – C2b = 4,700 pF (Vicor Part # 01000)

C 3a – C3b = 0.01 µF (Vicor Part # 04872)

C4 = 2.2 µF

L1 = 20 µH

L2 = 20 µH

+

IN

GATE
IN

GATE
OUT

–IN

+OUT

+S

T

RIM

–

S

–OUT

C

onditions

Light Load = 3 A

Nominal Load = 15 A

Full Load = 30 A

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

Differential-Mode Noise Filter. Differential-mode
conducted noise current is the component of current,
at the input power pin, which is opposite in direction or

hase with respect to the other input power pin.

p

All Vicor converters have an internal differential-mode LC
filter which, in conjunction with a small external capacitor

C1 (minimum value in µF) = 400 / Vin,

reduces differential-mode conducted noise. The external
capacitor should be placed close to the module to reduce
loop cross-sectional area.

Differential-Mode Filter

Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output

Care should be taken to reduce the loop cross-sectional
area of differential-mode current flowing between the
source and C1. Since differential-mode input current is by

efinition opposite in phase, twisting the input leads

d
causes noise cancellation. PCB power planes can reduce

adiated noise if the traces are on opposite sides of the

r
PCB directly over one another. If differential mode inductance
is used, it may be common to one or more modules.

Conducted Noise vs. Load

3 Amp Load 15 Amp Load 30 Amp Load

Figure 9–5 — Conducted noise, differential-mode filtering

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 22 of 98

Apps. Eng. 800 927.9474 800 735.6200

L

C

Vs

Ip

+IN

–IN

Vp

+

OUT

–

OUT

Ceramic

Parasitic

Capacitance

Baseplate

Rectifier

Ceramic

FET

ShieldShield

Design Guide & Applications Manual

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

RADIATED NOISE

Radiated noise may be either electric field or magnetic
field. Magnetic radiation is caused by high di/dt and is
generally what is measured by FCC, VDE or MIL-STD-461.
Vicor converters utilize zero-current-switching, with the
advantage over PWM non-zero-current-switching being
that zero-current-switching topologies contain minimal
discontinuities in the switched current waveforms,
resulting in lower di/dt’s. Electric field radiation (caused by
dv/dt) is “near-field,” i.e., it decays rapidly as a function of
distance and as a result does not typically affect radiated
measurements.

Figure 9–6 — Basic zero-current-switching converter topology

Radiation can be minimized by proper board layout. Keep

(VI-200 / VI-J00)

all leads with AC current short, twisted or routed as
overlapping planes to minimize loop cross-sectional area.

Also keep in mind the effects of capacitive coupling —
even when not expected. Do not put an unshielded filter
on the opposite side of the PCB from the module.
Conducted noise can be capacitively coupled around the
filter. Do not route input and output leads in the same
cable bundle. Again, no special precautions, just good
design practice.

Since the energy in every pulse is related to the square of
the applied voltage (CV
as approximately the square of the line voltage. For
example, a 300 V input unit can vary from 200 – 400 V,
or a factor of two, therefore it follows that the repetition
rate must vary by approximately a factor of four to regulate
the output. As previously established, the current in the
primary is a half-wave rectified sine wave, but the voltage
on the primary is a square wave. Since this voltage is a
square wave, it contains harmonics of the fundamental

NOISE CONSIDERATIONS

switching frequency. It also includes frequencies, that extend
to 70 MHz.

All switchmode power supplies generate a certain amount
of “noise”, yet it remains one of the least understood
parameters in power conversion.

These frequencies can be of interest in the following
circumstances. Rapidly changing voltages (high dv/dt) can
generate E-fields (primarily near-field) which do not usually

VI-200s and VI-J00s both use the same topology, so their
operation is very similar. These products are zero-current­switching converters — i.e., the current is zero when the
main switch is turned on or off. While the switch is on,
the current through the switch or the primary of the
transformer is a half-wave rectified sine wave. Similar in
operation to a resonant converter, these products are
commonly referred to as quasi-resonant converters. The
LC resonant frequency is fixed so the on-time of the
switch is about 500 ns. When the switch turns on, energy
builds up in the leakage inductance of the transformer (L)
and then “transferred” into the capacitor on the
secondary side of the module. (C, Figure 9–6) The energy
processed in each pulse is fixed, and is ultimately the

2

energy stored in this capacitor, 1/2 CV

. Since the energy

cause system noise problems since they significantly
decrease as a function of distance. For this reason, E-fields
are not measured by agencies such as the FCC or VDE.
These agencies do, however, measure the magnetic
radiation caused by high frequency currents in a conductor.
The half-wave rectified sine wave in the transformer is an
example of this, but since there are minimal discontinuities
in the current waveform and the loop cross-sectional area
is very small, the resultant E-field is very small. E-fields can
be a problem if sensitive circuitry is located near the
module. In this case, a shield can be positioned under the
label side of the module as a discrete element or as a
ground plane on the PCB. The other effect that occurs as
a result of the 50 – 70 MHz component on the main
switch is common-mode noise. (Figure 9–7)

in every pulse is fixed, the repetition rate of the pulse train
is varied as a function of load to regulate the output
voltage. Maximum repetition rate occurs at minimum line,
full load and is approximately twice the LC time period or
1 µs. If the load drops by 50%, then the repetition rate is
approximately one-half of maximum (since the energy in
every pulse is fixed). Therefore the pulse repetition rate
varies linearly with load, to a first order approximation.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 23 of 98

Apps. Eng. 800 927.9474 800 735.6200

Figure 9–7 — The shield layer serves to reduce the capacitance

9. EMC Considerations

2

), the pulse repetition rate varies

C

FET

C

Rectifier

I

CM

C

FET

C

Rectifier

C

External

C

External

I

CM

Primary Secondary

V

p

V

p

V

p

Baseplate

I

DM

Y

caps Ycaps

9. EMC Considerations

To Scope

Ground Ring on Probe

T

o Scope

or

I

nsert probe into female receptacle
(Vicor P/N 06207) for proper output
d

ifferential noise measurement technique

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

The dv/dt of the switch (FET) is a noise generator. This
FET is mounted on a two layer insulating and shielding
assembly which is attached to the baseplate. Since ceramic

s a dielectric, there is capacitance from the FET to the

i
baseplate. (Figure 9–7) The output rectifiers are also tied

o the baseplate with ceramic insulators, adding additional

t
capacitance. The dv/dt of the FET is differentiated by these
two series capacitors, resulting in a spike of noise current
at 50 – 70 MHz that flows from primary to secondary.
(Figure 9–8) This noise current is common-mode as opposed
to differential, and therefore should not affect the operation
of the system. It should be noted, however, that oscilloscopes
have a finite ability to reject common-mode signals, and
these signals can be abnormally emphasized by the use of
long ground leads on the scope probe.

have very short leads since the frequency is high. It must
also be a good capacitor (i.e., ceramic or other material
that has a low ESR / ESL). This type of capacitor is most

mportant on high input voltage units since the “dv”

i
is larger, but is required for all units. For off-line

pplications this capacitor must have the appropriate

a
safety agency approvals.

Figure 9–9 — Output ripple measurement technique

A capacitor from +/–Vout to the baseplate, is required
since the output rectifier has a changing voltage on it,
and, like the FET, can generate common-mode noise.
This capacitor is similarly recommended for high output
voltage units (48 V).

Figure 9–8 — Noise coupling model

MEASURING OUTPUT NOISE

Long ground leads adversely impact the common-mode
rejection capability of oscilloscopes because the ground
lead has inductance not present on the signal lead. These
differing impedances take common-mode signals and
convert them to differential signals that show up on the
trace. To check for common-mode noise, place the
oscilloscope probe on the ground lead connection of the
probe while the ground lead is tied to output return.
(Figure 9–9) If the noise is common-mode, there will still
be “noise” observed at the same test point.

: The output return must be at the same relative

NOTE
potential as the earth ground of the oscilloscope or

ground lead.

Capacitors are required from the +/–IN to the baseplate

damaging current may flow through the oscilloscope

thereby shunting common-mode current, thus reducing
noise current on the input power lines. The capacitor must

Common-mode noise is not differential with respect to
the output. It does, however, flow in both input and
output leads of the power supply and is a noise parameter
that is measured by the FCC or VDE. It can cause power
systems to fail radiated emission tests, so it must be dealt
with. Bypass capacitors to the baseplate with a common­mode filter on the input of the module or the main input
of the power supply is required.

The common-mode filter is typically placed on the input as
opposed to the output. Theoretically, since this current
flows from primary to secondary, the choke could be
placed in either the input or the output, but is preferably
placed in the input leads for the following reasons:

1) input currents are smaller since the input voltage is
usually higher;

2) line regulation of the module can correct for voltage
drops across the choke; and

3) if the choke is on the output and the senses are
connected to the other side of it, the stability of the
loop may be impacted.

Differential output noise is the AC component of the
output voltage that is not common to both outputs. The
noise is comprised of both low frequency, line-related
noise (typically 120 Hz) and high frequency switching noise.

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 24 of 98

Apps. Eng. 800 927.9474 800 735.6200

Design Guide & Applications Manual

+IN

–IN

+OUT

–OUT

C2

a

C1

C3

a

C2

b

C3

b

GATE
OUT

GATE
IN

+S

TRIM

–S

C1 = 100 µF
C2a – C2b = 4,700 pF (Vicor Part # 01000)
C3a – C3b = 0.01 µF (Vicor Part # 04872)

Conditions

Light Load = 3 A
Nominal Load = 15 A
Full Load = 30 A

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

9. EMC Considerations

High Frequency Switching Noise. Peak-to-peak output
voltage ripple is typically 2% or less (1% for 12 V outputs
and above). Hence additional output filtering is generally

ot required. Digital systems rarely need additional

n
filtering. However some analog systems, such as

ltrasound systems, will probably require additional output

u
filtering. See additional output filter choices in Table 9–1.

Line Related Output Noise. Line related output noise
can be determined from the converter specification —
Input Ripple Rejection. As an example, a VI-260-CV

(300 Vin to 5 Vout) has a rejection specification at 120 Hz
of 30 + 20 Log (Vin / Vout). Vin = 300 and Vout = 5,
hence its rejection is 30 + 35.56 = 65.56 dB, which

rovides an attenuation factor of 1.89 k. Therefore, if the

p
input to the converter has 30 V p-p of ripple, the output

-p ripple would be 15.8 mV. It is not practical to

p
attenuate this component further with passive filtering
due to its low frequency, hence active filtering is required.
The RAM contains both a passive filter for high frequency
noise and an active filter for low frequency noise.

5 V Outputs 12 – 15 V Outputs 24 – 48 V Outputs

No Additional Filter 2% p-p (Typical) 1% p-p (Typical) 0.2% p-p (Typical)
Low ESR Output Cap. 1% p-p (Typical) 0.5% p-p (Typical) 0.1% p-p (Typical)
LC Output Filter 0.4% p-p (Typical) 0.2% p-p (Typical) 0.05% p-p (Typical)
RAM Filter (VI-200) <3 mV p-p (Maximum) <3 mV p-p (Maximum) <3 mV p-p (Maximum)
RAM Filter (VI-J00) <10 mV (Maximum) <10 mV (Maximum) <10 mV (Maximum)

Table 9–1 — Output filter options and output voltage and ripple

Differential Output Filtering

Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output

Output Ripple vs. Load

3 Amp Load 15 Amp Load 30 Amp Load

Figure 9–10 — Output noise, no additional output filtering

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 25 of 98

Apps. Eng. 800 927.9474 800 735.6200

9. EMC Considerations

+

IN

–

IN

+OUT

–OUT

C3

a

G

AT E

IN
GAT E

OUT

+

S

TRIM

–

S

C4

C

2

a

C1

C

2

b

C3

b

C1 = 100 µF

C 2a – C2b = 4,700 pF (Vicor Part # 01000)

C 3

a

– C3

b

=

0.01 µF (Vicor Part # 04872)

C4 = 270 µF (Tant.)

Conditions

Light Load = 3 A
Nominal Load = 15 A
Full Load = 30 A

NOTE: A low ESR capacitor should be used on the output, preferably tantalum.

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Addition of Output Capacitor

Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output

Output Ripple vs. Load

Design Guide & Applications Manual

3 Amp Load 15 Amp Load 30 Amp Load

Figure 9–11 — Output noise, additional output capacitance

Apps. Eng. 800 927.9474 800 735.6200

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 26 of 98

Design Guide & Applications Manual

C1 = 100 µF
C2a – C2b = 4,700 pF (Vicor Part # 01000)
C3a – C3b = 0.01 µF (Vicor Part # 04872)

C4 = 270 µF (Ta n t .)

L1 = 200 nH (Vicor Part # 30268)

Conditions

Light Load = 3 A
Nominal Load = 15 A
Full Load = 30 A

+

IN

–

IN

+OUT

–OUT

C3

a

GATE
I

N

GATE
OUT

+

S

T

RIM

–S

C2

a

C1

C

2

b

C3

b

C

4

L

1

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output

9. EMC Considerations

LC Output Filter

Output Ripple vs. Load

3 Amp Load 15 Amp Load 30 Amp Load

Figure 9 –12 — Output noise, additional output inductor and capacitor (L-C Filter)

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 27 of 98

Apps. Eng. 800 927.9474 800 735.6200

9. EMC Considerations

C1 = 100 µF
C2a – C2b = 4,700 pF (Vicor Part # 01000)
C3a – C3b = 0.01 µF (Vicor Part # 33643)
C4 = 220 µF (Electrolytic)

Conditions

Light Load = 3 A
Full Load = 15 A
Overload Condition = 30 A

+IN

–IN

+OUT

–OUT

C3

a

C3

b

GATE
IN

GATE
OUT

+S

TRIM

–S

C2

a

C2

b

C1

+IN

–IN

–OUT

–S IN

+S IN

+OUT

RAM

+S

–S

+

–

L1

C4

+

CM

RAM / MI-RAM OPERATION

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

Design Guide & Applications Manual

The RAM / MI-RAM attenuates output noise in two ways.
First, an LC filter in the RAM/ MI-RAM attenuates high
frequency components associated with the switching
frequency. Secondly, the RAM/ MI-RAM contains an active
filter that attenuates low frequency components associated
with the input to the converter. These frequencies are on
the order of 60 – 120 Hz and harmonics would require
very large output LC if a passive approach were to be
used. Essentially, the active circuit looks at the output
ripple from the converter, multiplies it by –1 (inverts) and
adds it to the output. This effectively cancels out the low
frequency components.

The RAM does not contain any common-mode filtering,
so whatever common-mode noise is present is passed
through. It only provides differential filtering of noise that
is present on one output pin relative to the other.

RAM Output Filter

Typical Vicor Module (VI-230-CV) 48 V Input, 5 V Output with VI-RAM-C2

The use of the RAM / MI-RAM is very straightforward, but
a couple of precautions should be noted. The LC filter is in
the positive output lead, so if that lead is shorted then the
high frequency attenuation is compromised. The active
circuit is in the negative output lead, so if that lead is
shorted the low frequency attenuation is compromised.
The RAM must be used with a common-mode choke at
the input of the converter.

The RAM is intended to be used with the Vicor VI-200 /
VI-J00, and the MI-RAM is intended to be used with Vicor
MI-200/ MI-J00 Family of DC-DC converter modules. It is
also available in a chassis mounted version as VI-LRAM-xx
(MegaMod package) or VI-RAM-xx-B1 (BusMod package).

NOTE: Do not use if load is inductive as instability
may result. The addition of the RAM will increase the
converter’s current limit setpoint by ~ 14%.

Output Ripple vs. Load

3 Amp Load 15 Amp Load

Figure 9–13 — Output noise, with Ripple Attenuator Module (RAM)

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 28 of 98

Apps. Eng. 800 927.9474 800 735.6200

30 Amp Load

(Overload Condition)

Design Guide & Applications Manual

–OUT

–S

+S

+

OUT

+

IN

GATE
I

N

GATE
OUT

–IN

TRIM

L1

C1

C2

or VI-200 and VI-J00 Family DC-DC Converters and Configurable Power Supplies

F

10. Optional Output Filters

OVERVIEW

The LC filter design below is a comparatively simple solution
for reducing ripple on the outputs of Vicor’s VI-200 and
VI-J00 Family converter modules. These components are

mall and provide significant peak-to-peak noise attenuation.

s
Since an output filter capacitor is already present in the
DC-DC converter, adding an inductor and capacitor to the
output creates a pi filter. It is important that the inductor
wire be of a size sufficient to carry the load current,
including a safety factor, and that the core does not
saturate. LC filters are generally needed only where very
accurate analog signals are involved.

The RAM/MI-RAM (Ripple Attenuator Module) should be
used if greater attenuation of output ripple is required, or
where additional AC power line ripple frequency rejection
is required.

All standard outputs will function with either remote sense
or local sense, with the recommended capacitance. Lower
ESR is achieved with capacitors in parallel. Ripple data
measured at 20 MHz bandwidth limit.

Adding excessive amounts of external filtering may
compromise the stability of the converter and result in
oscillation.

FILTER COMPONENTS FOR 5 V OUTPUT

• L1 — Vicor P/N 30268 or Micrometals #T38-26/90 core
with 2T #14 wire (200 nH)

C1, C2 — Vicor P/N 30800, 270 µF / 10 V,

•
solid tantalum, ESR 90 m

Ω typical

• Typical data at high line input:
With full load, ripple ~ 11 mV p-p
With 50% load, ripple ~ 8 mV p-p

FILTER COMPONENTS FOR 12 V AND 15 V OUTPUTS

• L1 — Vicor P/N 30268 or Micrometals #T38-26/90 core
with 2T #14 wire (200 nH)

• C1, C2 — Vicor P/N 30506, 120 µF / 20 V,
solid tantalum, ESR 90 mΩ typical

• Typical data at high line input:
With full load, ripple ~ 5 mV p-p
With 10% load, ripple ~ 15 mV p-p

FILTER COMPONENTS FOR 24 V AND 28 V OUTPUTS

• L1 — Vicor P/N 30268 or Micrometals #T38-26/90 core
with 2T #14 wire (200 nH)

Figure 10 –1 — Recommended LC output filter

• C1, C2 — Vicor P/N 30507, 68 µF / 30 V,
solid tantalum, ESR 160 mΩ typical

• Typical data at high line input:
With full load, ripple ~ 6 mV p-p
With 10% load, ripple ~ 18 mV p-p

VI-200 and VI-J00 Family Design Guide Rev 3.5 vicorpower.com

Page 29 of 98

Apps. Eng. 800 927.9474 800 735.6200