DEMO MANUAL DC2378A-A
LTM4650
High Efficiency, Single 50A or Dual 25A
Step-Down Power µModule Regulator
Description
Demonstration circuit DC2378A-A features the
LTM
®
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
for certain V
IN
, V
OUT
, and thermal conditions. The board
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
®
operation in less
noise sensitive applications. Two outputs can be connected
in parallel for a single 50A output solution with optional
jumper resistors. The board allows the user to program
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
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DEMO MANUAL DC2378A-A
performance summary
PARAMETER
Input Voltage Range
Output Voltage V
OUT1
Output Voltage V
OUT2
Per-Channel Maximum Continuous Output
Current
Default Operating Frequency
Resistor Programmable Frequency Range
External Clock Sync. Frequency Range
Efficiency of Channel 1
Efficiency of Channel 2
Load Transient of Channel1
Load Transient of Channel2
V
IN
= 12V, V
OUT1
= 1.5V, I
OUT1
= 25A, f
SW
= 500kHz
V
IN
= 12V, V
OUT2
= 1V, I
OUT2
= 25A, f
SW
= 500kHz
V
IN
= 12V, V
OUT1
= 1.5V, I
STEP
= 12.5A ~ 18.75A
V
IN
= 12V, V
OUT2
= 1V, I
STEP
= 12.5A ~ 18.75A
250
400
88.8
See Figure 4
86.5
See Figure 5
See Figure 6
See Figure 7
V
IN
= 4.5V ~ 15V, I
OUT1
= 0A ~ 25A, JP1: CCM
V
IN
= 4.5V ~ 15V, I
OUT2
= 0A ~ 25A, JP1: CCM
Derating Is Necessary for Certain V
IN
, V
OUT
and
Thermal Conditions, See Data Sheet for Detail.
CONDITIONS
Specifications are at T
A
= 25°C
MIN
4.5
1.5 ±1.5%
1 ±1.5%
25
(Per-Channel)
500
780
780
TYP
MAX
15
UNITS
V
V
V
A
kHz
kHz
kHz
%
%
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
MODE
CCM
JP2
RUN1
ON
JP3
RUN2
ON
JP4
TRACK1
SEL.
SOFT-
START
JP5
TRACK2
SEL.
SOFT-
START
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 soft-
start 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
OUT
= 0.6V(1 + 60.4k/R25).
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2. With power off, connect the input power supply, load
and meters as shown in Figure 2. Preset the load to 0A
and V
IN
supply to 12V.
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.
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DEMO MANUAL DC2378A-A
Quick start proceDure
Figure 2. Test Setup of DC2378A-A
+
V
OUT
C
OUT
GND
–
Figure 3. Measuring Output Voltage Ripple
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DEMO MANUAL DC2378A-A
Quick start proceDure
95
5V
IN
, 1.5V
O
95
5V
IN
, 1V
O
90
EFFICIENCY (%)
12V
IN
, 1.5V
O
85
12V
IN
, 1V
O
90
EFFICIENCY (%)
85
80
80
75
75
70
0
5
10
20
15
OUTPUT LOAD CURRENT (A)
25
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70
0
5
10
20
15
OUTPUT LOAD CURRENT (A)
25
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Figure 4. Measured Efficiency on Channel 1
(V
OUT1
= 1.5V, f
SW
= 500kHz, Channel 2 Disabled)
Figure 5. Measured Efficiency on Channel 2
(V
OUT2
= 1V, f
SW
= 500kHz, Channel 1 Disabled)
1.5V OUTPUT (20MHz BW) [20mV/DIV]
1V OUTPUT (20MHz BW) [20mV/DIV]
12.5V TO 18.75A
12.5V TO 18.75A
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Figure 6. Measured Channel 1 12.5A to 18.75A Load Transient
(V
IN
= 12V, V
OUT1
= 1.5V)
Figure 7. Measured Channel 2 12.5A to 18.75A Load Transient
(V
IN
= 12V, V
OUT2
= 1V)
4
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DEMO MANUAL DC2378A-A
Quick start proceDure
1.5V OUTPUT (20MHz BW) [20mV/DIV]
1V OUTPUT (20MHz BW) [20mV/DIV]
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Figure 8. Measured Output Voltage Ripple at 12V Input,
1.5V/25A with Standard Demo Circuit Default Setup
Figure 9. Measured Output Voltage Ripple at 12V Input,
1V/25A with Standard Demo Circuit Default Setup
Figure 10. Thermal Capture at 12V
IN
, 1.5V
OUT
at 25A and 1V
OUT
at 25A
(Ambient Temperature = 23°C, 200 LFM Airflow and No Heat Sink)
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