1
dc1997a-af
DEMO MANUAL
DC1997A-A/DC1997A-B
DESCRIPTION
LTC3838EUHF-1/
LTC3838EUHF-2
High Current, Dual Output
Synchronous Buck Converter
Demonstration circuits
dual output synchronous buck converters featuring the
. Both assemblies
provide two outputs of 1.5V/20A and 1.2V/20A over an
input voltage range of 4.5V to 14V at a switching frequency
of 300kHz.
Applications requiring the output to be adjusted with an
external reference can be implemented with the DC1997A-B
assembly. Such applications include adaptive voltage scal-
ing optimization (AVSO) where the processor voltage is
adjusted to achieve optimal efficiency, wide output voltage
applications controlled by a DAC, or margining. The 2nd
channel of the DC1997A-B assembly is regulated to an
onboard 1.2V reference in the default setup. The same
reference can be set from 0.8V to 1.5V with a potentiometer
or the 2nd channel can regulate to a source external to the
board. The 1st channel on the DC1997A-B assembly and
both channels on the DC1997A-A version are regulated
to the internal reference.
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
The entire converter, excluding the bulk input and output
capacitors, fits within a 1.5in
2
area on the board. The high
density is a result of the compact, 2-sided drop-in layout
and the use of dual channel FETs.
Additional features of this demo board include:
• Remote sensing for each output.
• PLLIN and CLKOUT pins.
• PGOOD, RUN and TRK/SS pins for each output.
• Optional resistors to tie the two outputs together.
• Optional footprint for discrete single channel FETs for
higher output current.
• Optional footprints to implement DTR (detect transient)
to reduce overshoot following a load release.
Design files for this circuit board are available at
http://www.linear.com/demo
PERFORMANCE SUMMARY
Specifications are at T
A
= 25°C, No Airflow
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
4.5V
Maximum Input Voltage
14V
Output Voltage V
OUT1
I
OUT1
= 0A to 20A, V
IN
= 4.5V to 14V
1.5V ± 2%
Output Voltage V
OUT2
I
OUT2
= 0A to 20A, V
IN
= 4.5V to 14V
1.2V ± 2%
V
OUT1
Maximum Output Current, I
OUT1
V
IN
= 4.5V to 14V, V
OUT1
= 1.5V
20A
V
OUT2
Maximum Output Current, I
OUT2
V
IN
= 4.5V to 14V, V
OUT2
= 1.2V
20A
Nominal Switching Frequency
300kHz
Efficiency (Measured on DC1997A-B Assembly)
See Figure 2
V
OUT1
= 1.5V, I
OUT1
= 20A, V
IN
= 12V
90.4% Typical
V
OUT2
= 1.2V, I
OUT2
= 20A, V
IN
= 12V
88.8% Typical
