DEMO MANUAL DC2132A
LT3081, LT8612, LT3092
24V 3A Constant Voltage,
Constant Current Bench Supply
Description
DC2132A is a 24V 3A constant voltage, constant current
bench supply. It regulates any output voltage from 0V to
24V and any output current from 0A to 3A. It runs from
10V to 40V input although the output voltage should remain
5V or more below the input voltage.
The
LT
®
8612
step-down regulator is followed by two parallel
LT
®
3081
linear regulators for a combination of low output
ripple, high bandwidth and easy-to-adjust output voltage
and current limits. The LT8612 is configured in pulse-
skipping operation and its output voltage is regulated to
roughly 1.7V above the output voltage of the LT3081. The
LT3081 SET and I
LIM
pins are connected to potentiometers
that act as adjustable knobs on the PCB for voltage and
current limit respectively.
The
LT
®
3092
current source is used to deliver current to
power the adjustable resistance of the voltage limit knob
(potentiometer). That voltage directly sets the output volt-
age of the LT3081. The maximum output voltage can be
set to three settings: 24V, 15V and 5.5V with the shunt
position on JP1. The setting should be changed according
to the choice of input voltage. A 36V, 24V, or 12V AC/DC
converter can be used to power this supply (as well as
any DC voltage between 10V and 40V.) If input voltage
limits maximum output voltage, then it is recommended
to adjust the maximum output voltage to get the full range
of the adjustment knob for best resolution.
DC2132A operates to 0V and 0A. It is short-circuit proof.
With very small output capacitance, the short-circuit spike
is hundreds of times shorter in duration than commonly
used and expensive laboratory bench power supplies.
With the LT3081s in parallel on the output of this supply,
small output capacitance makes this possible. Only 30μF
is needed on the output of each LT3081. The LT3081 pro-
vides very low output ripple and short-circuit robustness.
An ON/OFF switch turns the converter and its components
on and off. A green indicator LED tells if the circuit is
on or not. Two TEMP turrets and an I
MON
turret provide
readouts of the LT3081 IC temperatures and the bench
supply output current.
The LT3081, LT8612, and LT3092 data sheets give com-
plete descriptions of the devices, operation and applications
information. The data sheet must be read in conjunction
with this demo manual for DC2132A. The LT3081ER is as-
sembled in a 7-lead plastic DD (R) package with a thermally
enhanced V
OUT
tab and with
θ
JA
= 15ºC/W. Proper board
layout is essential for maximum thermal performance. See
the the Layout Considerations section in the data sheet.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2132A
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.
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DEMO MANUAL DC2132A
Quick start proceDure
DC2132A is easy to set up to evaluate the performance
of the LT3081 and LT8612. Follow the procedure below:
1. Set the ON/OFF switch to OFF to disable switching.
2. With power off, connect the input power supply to
the V
IN
and GND terminals. Make sure that the V
IN
DC
input voltage will not exceed 40V. Be careful for hot
plug transients above 40V.
3. The DC2132A bench supply is robust and can be turned
on with or without a load. If the load is too big, DC2132A
will limit its output. If there is a short-circuit on the
output, DC2132A will run through the short safely and
will limit its current to its I
LIMIT
setting.
4. Observe the output voltage and current as well as the
temperature of the ICs.
Figure 1. Test Procedure Setup Drawing for DC2132A
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Embedded System
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