Linear LTM4650 Demo Manual

Description

DEMO MANUAL DC2378A-A

LTM4650

High Efficiency, Single 50A or Dual 25A

Step-Down Power µModule Regulator

Demonstration circuit DC2378A-A features the LT M®4650EY,
the high efficiency, high density, dual 25A, single 50A,
switch mode step-down power module regulator. The
input voltage is from 4.5V to 15V. The output voltage is
programmable from 0.6V to 1.8V. DC2378A-A can deliver
25A maximum current from each channel. As explained
in the data sheet, output current derating is necessary

, V

for certain V
operates in continuous conduction mode in heavy load
conditions. For high efficiency at low load currents, the
MODE jumper (JP1) selects pulse-skipping mode for noise
sensitive applications or Burst Mode
noise sensitive applications. Tw o outputs can be connected
in parallel for a single 50A output solution with optional
jumper resistors. The board allows the user to program

IN

, and thermal conditions. The board

OUT

®

operation in less

how its output ramps up and down through the TRACK/
SS pin. The output can be set up to either coincidentally or
ratiometrically track with another supply’s output. Remote
output voltage sensing is available for improved output
voltage regulation at the load point. These features and
the availability of the LTM4650EY in a compact 15mm ×
15mm × 5.01mm BGA package make it ideal for use in
many high density point-of-load regulation applications.
The LTM4650 data sheet must be read in conjunction with
this demo manual for working on or modifying the demo
circuit DC2378A-A.

Design files for this circuit board are available at

http://www.linear.com/demo/DC2378A-A

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.

Figure 1. LTM4650/DC2378A-A Demo Board

dc2378aaf

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DEMO MANUAL DC2378A-A

performance summary

PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Voltage Range 4.5 15 V

Output Voltage V

Output Voltage V

Per-Channel Maximum Continuous Output
Current

Default Operating Frequency 500 kHz

Resistor Programmable Frequency Range 250 780 kHz

External Clock Sync. Frequency Range 400 780 kHz

Efficiency of Channel 1 V

Efficiency of Channel 2 V

Load Transient of Channel1 V

Load Transient of Channel2 V

VIN = 4.5V ~ 15V, I

OUT1

VIN = 4.5V ~ 15V, I

OUT2

Derating Is Necessary for Certain V
Thermal Conditions, See Data Sheet for Detail.

= 12V, V

IN

= 12V, V

IN

= 12V, V

IN

= 12V, V

IN

Specifications are at TA = 25°C

= 0A ~ 25A, JP1: CCM 1.5 ±1.5% V

OUT1

= 0A ~ 25A, JP1: CCM 1 ±1.5% V

OUT2

, V

and

IN

OUT

OUT1

OUT2

OUT1

OUT2

= 1.5V, I

= 1V, I

= 1.5V, I

= 1V, I

= 25A, fSW = 500kHz 88.8

OUT1

= 25A, fSW = 500kHz 86.5

OUT2

= 12.5A ~ 18.75A See Figure 6

STEP

= 12.5A ~ 18.75A See Figure 7

STEP

25

(Per-Channel)

%

See Figure 4

%

See Figure 5

Quick start proceDure

Demonstration circuit DC2378A-A is easy to set up to
evaluate the performance of the LTM4650EY. Please refer
to Figure 2 for proper measurement setup and follow the
procedure below:

1. Place jumpers in the following positions for a typical
application:

JP1 JP2 JP3 JP4 JP5

MODE RUN1 RUN2 TRACK1

CCM

ON ON SOFT-

SEL.

START

TRACK2

SEL.

SOFT-

START

2. With power off, connect the input power supply, load
and meters as shown in Figure 2. Preset the load to 0A
and V

supply to 12V.

IN

3. Turn on the power supply at the input. The output
voltage in channel 1 should be 1.5V ±1.5% (1.4775V
~ 1.5225V) and the output voltage in channel 2 should
be 1V ±1.5% (0.985V ~ 1.015V).

4. Once the proper output voltage is established, adjust the
load within the operating range and observe the output
voltage regulation, output voltage ripple, efficiency and
other parameters. Output ripple should be measured
at J1 and J2 with BNC cables. 50Ω termination should
be set on the oscilloscope or BNC cables.

5. (Optional) For optional load transient test, apply an
adjustable pulse signal between IOSTEP CLK and GND
test point. Pulse amplitude (3V ~ 3.5V) sets the load
step current amplitude. The output transient current
can be monitored at the BNC connector J3 (10mV/A).
The pulse signal should have very small duty cycle (<
1%) to limit the thermal stress on the transient load
circuit. Switch the jumper resistors R34 or R35 (on the
backside of boards) to apply load transient

on channel

1 or channel 2 correspondingly.

6.

(Optional) LTM4650 can be synchronized to an external

clock signal. Place the JP1 jumper on EXT_CLK and
apply a clock signal (0V ~ 5V, square wave) on the
CLKIN test point.

7. (Optional) The outputs of LTM4650 can track another
supply. The jumpers JP4 and JP5 allow choosing soft­start or output tracking. If tracking external voltage is
selected, the corresponding test points, TRACK1 and
TRACK2, need to be connected to a valid voltage signal.

8. (Optional) LTM4650 can be configured for a 2-phase
single output at up to 50A on DC2378A-A. Install 0Ω
resistors on R14, R17, R28, R39, R43, R44, R45 and
remove R7, R19. Output voltage is set by R25 based
on equation V

= 0.6V(1 + 60.4k/R25).

OUT

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A

2

Quick start proceDure

OUT

DEMO MANUAL DC2378A-A

Figure 2. Test Setup of DC2378A-A

+ –

Figure 3. Measuring Output Voltage Ripple

C

OUT

V

GND

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