1
dc1626afa
DEMO MANUAL DC1626A
DESCRIPTION
LTC3838EFE
Wide Input Range, High Efficiency
Step-Down DC/DC Converter
Demonstration circuit 1626A is a dual output 1.5V/15A
and 1.2V/15A synchronous buck converter operating with
a switching frequency of 300kHz over an input voltage
range of 4.5V to 26V. The demo board comes in two ver-
sions. The -A version uses inductor DCR current sensing
with an iron powder inductor for high efficiency. The -B
version uses a 2.5mΩ sense resistor for accurate current
sensing with a low DCR ferrite inductor. The fixed on-time
valley current mode architecture of the LTC3838 allows for
a fast load step response (see Figures 6 to 9). The load
step response can be tested with the on-board load step
circuit and a bench pulse generator.
The demo board uses a high density, two sided drop-in
layout. The entire converter, excluding the bulk output and
input capacitors, fits within a compact 1.5"
×
1.0" area
on the board. The package style for the LTC3838EFE is a
38-lead TSSOP with an exposed ground pad.
L
, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY
The main features of the board are listed below:
• MODE jumper to program either DCM or FCM at light
or no load
• EXTVCC pin
• PLLIN pin to synchronize the converter to an external
clock
• Remote sensing for V
OUT1
• Optional resistors to tie the two phases together
• Each rail has its own RUN pin, PGOOD pin and
TRACK/SS pin
Design files for this circuit board are available at
http://www.linear.com/demo
(T
A
= 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
4.5V
Maximum Input Voltage
26V
Output Voltage V
OUT1
I
OUT1
= 0A to 15A, V
IN
= 4.5V to 26V
1.2V ±2%
Output Voltage V
OUT2
I
OUT2
= 0A to 15A, V
IN
= 4.5V to 26V
1.5V ±2%
V
OUT1
Maximum Output Current, I
OUT1
V
IN
= 4.5V to 26V, V
OUT1
= 1.2V
15A
V
OUT2
Maximum Output Current, I
OUT2
V
IN
= 4.5V to 26V, V
OUT2
= 1.5V
15A
Nominal Switching Frequency
300kHz
-A Efficiency
See Figures 2 and 3
V
OUT1
= 1.2V, I
OUT1
= 15A, V
IN
= 12V
89.1% Typical
V
OUT2
= 1.5V, I
OUT2
= 15A, V
IN
= 12V
90.2% Typical
-B Efficiency
See Figures 4 and 5
V
OUT1
= 1.2V, I
OUT1
= 15A, V
IN
= 12V
85.9%
V
OUT2
= 1.5V, I
OUT2
= 15A, V
IN
= 12V
88.2%
