VICOR URAM3TS3, URAM3TS1, URAM3TN3, URAM3TN2, URAM3TN1 Datasheet

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Vicor Corp. Tel: [phone] Fax: [phone] MicroRAM Rev. 1.1 Page 1 of 8

Features

• >40dB ripple attenuation from

60Hz to 1MHz

• Integrated OR’ing diode supports

N+1 redundancy

• Significantly improves load

transient response

• Efficiency up to 98%

• User selectable performance optimization

• Combined active and passive filtering

• 3-30Vdc input range

• 20 and 30 Ampere ratings

Product Highlights

Vicor’s MicroRAM output ripple attenuation
module combines both active and passive
filtering to achieve greater than 40dB of
noise attenuation from 60Hz to 1Mhz. The
MicroRAM operates over a range of 3 to
30Vdc, is available in either 20 or 30A
models and is compatible with most
manufacturers switching converters
including Vicor’s 1st and 2nd Generation
DC-DC converters.

The MicroRAM’s closed loop architecture
greatly improves load transient response and
with dual mode control, insures precise point
of load voltage regulation, The MicroRAM
supports redundant and parallel operation
with its integrated OR’ing diode function.

It is available in Vicor’s standard micro
package (quarter brick) with a variety of
terminations for through hole, socket or
surface mount applications.

Data Sheet

MicroRAM

TM

Output Ripple Attenuation Module

45

Shown actual size:

2.28 x 1.45 x 0.5 in

57,9 x 36,8 x 12,7 mm

Absolute Maximum Ratings

Thermal Resistance

Parameter Typ Unit

Baseplate to sink; flat, greased surface 0.16 °C/Watt
Baseplate to sink; with thermal pad (P/N 20264) 0.14 °C/Watt
Baseplate to ambient 8.0 °C/Watt
Baseplate to ambient; 1000 LFM 1.9 °C/Watt

uRAM 2 C 2 1

Product

Baseplate
1 = Slotted
2 = Threaded
3 = Thru-hole

Pin Style*
1 = Short Pin
2 = Long Pin
S = Short ModuMate
N = Long ModuMate

Product Grade
C = –20°C to +100°C
T = –40°C to +100°C
H = –40°C to +100°C
M = –55°C to +100°C

Type
2=20A
3=30A

Part Numbering

*Pin styles S & N are compatible with the ModuMate interconnect system for socketing and surface mounting.

Patents Pending

Parameter Rating Unit Notes

+In to –In 30 Vdc Continuous
+In to –In 40 Vdc 100ms
Load current 40 Adc Continuous
Ripple Input (Vp-p) 100 mV 60Hzc100 kHz
Ripple Input (Vp-p) 500 mV 100kHz–2MHz
Mounting torque 4-6 (0.45-0.68) In. lbs (Nm) 6 each, 4-40 screw
Pin soldering temperature 500 (260) °F (°C) 5 sec; wave solder
Pin soldering temperature 750 (390) °F (°C) 7 sec; wave solder
Storage temperature (C, T-Grade) -40 to +125 °C
Storage temperature (H-Grade) -55 to +125 °C
Storage temperature (M-Grade) -65 to +125 °C
Operating temperature (C-Grade) -20 to +100 °C Baseplate
Operating temperature (T, H-Grade) -40 to +100 °C Baseplate
Operating temperature (M-Grade) -55 to +100 °C Baseplate

Vicor Corp. Tel: [phone] Fax: [phone] MicroRAM Data Sheet Rev. 1.1 Page 2 of 8

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Parameter Min Typ Max Unit Notes

Operating current range No internal current limiting. Converter input must be

µRAM2xxx 0.02 20 A properly fused such that the µRAM output current
µRAM3xxx 0.02 30 A does not exceed the maximum operating current

rating by more than 30% under a steady state condition.
Operating input voltage 3.0 30 Vdc Continuous
Transient output response

50 mVp-p

Step load change;
Load current step <1A/µsec see Figures 9, 12, & 15, pp. 6-7

Transient output response Optional capacitance C

TRAN can be used

Load current step <1A/µsec 50 mVp-p to increase transient current capability; See Figures
(CTRAN = 820µF) 1 & 2 on p. 3 and Figures 10, 13, & 16 on pp. 6-7

V

HR headroom voltage range

(1)

See Figures 5, 6 & 7
@ 1A load

325 425 mV

See Table 1 for headroom setting resistor values
Output ripple 10 mVp-p Ripple frequency 60Hz to 100kHz; optional capacitor

Input Vp-p = 100mV 5 mVrms C

HR = 100µF required to increase low frequency

attenuation as shown in Figures 3a and 3b

see Figures 8, 11, & 14, pp. 6-7
Output ripple 10 mVp-p Ripple frequency 100kHz to 2MHz;

Input Vp-p = 500mV 5 mVrms see Figures 8, 11, & 14, pp. 6-7
SC output voltage

(2)

1.23 Vdc See Table 1 R

SC value

OR’ing threshold 10 mV Vin – Vout
µRAM bias current 60 mA
Power Dissipation

µRAM2xxx V

HR = 380mV@1A 7.5 W Vin = 28V; Iout = 20A

µRAM3xxx V

HR = 380mV@1A 11.5 W Vin = 28V; Iout = 30A

µRAM MODULE SPECIFICATIONS (-20°C to +100°C baseplate temperature)

Electrical Characteristics

Electrical characteristics apply over the full operating range of input voltage, output power and baseplate temperature, unless
otherwise specified. All temperatures refer to the operating temperature at the center of the baseplate.

(1)

Headroom is the voltage difference between the +Input and +Output pins.

R

HR = (µRAM +Out/VHR) x 2.3k (see Table 1 for example values)

(2)

SC resistor is required to trim the converter output up to accommodate the headroom of the µRAM module when remote sense
is not used. This feature can only be used when the trim reference of the converter is in the 1.21 to 1.25 Volt range.
(see Table 1 with calculated R

SC resistor values)

R

SC = ((µRAM +Out)/1.23V x 1k) – 2k

µRAM Out

3.0V

5.0V

12.0V

15.0V

24.0V

28.0V

V

HR @ 1A

375mV
375mV
375mV
375mV
375mV
375mV

R

HR Value (ohms)

18.4k

30.6k

73.6k

92.0k

147.2k

171.7k

R

SC Value (ohms)

0.439k

2.07k

7.76k

10.20k

17.50k

20.76k

Table 1—RHR and RSC are computed values for a 375mV case. To compute different headroom voltages, or for standard resistor
values and tolerances, use Notes 1 and 2.

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Vicor Corp. Tel: [phone] Fax: [phone] MicroRAM Rev. 1.1 Page 3 of 8

Electrical Characteristics (continued)

APPLICATION SCHEMATIC DRAWINGS USING VICOR CONVERTERS AND THE µRAM

Figure 1—Typical Configuration using Remote Sensing

Figure 2—Typical Configuration using SC Control (Oppional C

HR 25µF maximum in SC configuration.)

Functional Description

The MicroRAM has an internal passive filter that
effectively attenuates ripple in the 50kHz to 1MHz range.
An active filter provides attenuation from low frequency
up to the 1MHz range. The user must set the headroom
voltage of the active block with the external R

HR resistor

to optimize performance. The MicroRAM must be connected
as shown in Figures 1 or 2 depending on the load sensing
method. The transient load current performance can be
increased by the addition of optional C

TRAN capacitance

to the C

TRAN pin. The low frequency ripple attenuation

can be increased by addition of optional C

HR capacitance

to the V

REF pin as shown in Figures 3a and 3b, on p. 5.

Transient load current is supplied by the internal CTRAN
capacitance, plus optional external capacitance, during the
time it takes the converter loop to respond to the increase
in load. The MicroRAM’s active loop responds in roughly
one microsecond to output voltage perturbations. There
are limitations to the magnitude and the rate of change of
the transient current that the MicroRAM can sustain while
the converter responds. See Figures 8-16, on pp. 6 and 7,
for examples of dynamic performance. A larger headroom
voltage setting will provide increased transient performance,
ripple attenuation and power dissipation while reducing
overall efficiency (see Figures 4a, 4b, 4c and 4d on p. 5).

RSENSE

(2)

+In

PC

DC-DC

Converter

PR

–In

+Out

+S

SC

–S

–Out

5.1

22µF

CTRAN*

*

Optional Component

+In

SC

TRAN

C

–In

µRAM

+Out

RHR

VREF

CHR*

–Out

+In

PC

PR

–In

DC-DC

Converter

+Out

RSC RHR

SC

–Out

*

+In

SC

TRAN

C

CTRAN*

Optional Component

–In

µRAM

+Out

VREF

–Out

C

HR*