2
Rev. 0
QUICK START PROCEDURE
Demonstration circuit 2543B is easy to set up to evaluate
the performance of the LTC7820. Refer to Figure 1 for
the proper measurement equipment setup and follow the
procedure below.
1. With power off, connect the input power supply to V
IN
(36V to 60V) and GND (input return).
2. Connect the output loads between V
OUT
and GND
(Initial load: no load). Refer to Figure 1.
3. Connect the DVMs to the input and output.
4. Check the default jumper/switch position: SW1 (RUN):
OFF; JP2 (BIAS): ON.
5. Turn on the input power supply and adjust voltage
to 48V.
NOTE: Make sure that the input voltage does not
exceed 60V.
6. Turn on the switches: SW1: ON.
7. Check for the proper output voltages from V
O_SNS
+
to
V
O_SNS
–
.
8. Once the proper output voltage is established, adjust
the loads within the operating range and measure the
efficiency, output ripple voltage and other parameters.
9. After completing all tests, adjust the load to 0A, power
off the input power supply.
Notes:
1. When measuring the output or input voltage ripple,
do not use the long ground lead on the oscilloscope
probe. See Figure 3 for the proper scope probe tech-
nique. Short, stiff leads need to be soldered to the (+)
and (–) terminals of an output capacitor. The probe’s
ground ring needs to touch the (–) lead and the probe
tip needs to touch the (+) lead.
2. When doing the load step test with the on-board
dynamic load circuit, please make sure the load step-
up pulse duty cycle does not exceed 2% and the pulse
duration is less than 500µs so that the temperature
of the MOSFETs Q9, Q23 in the dynamic load circuit
stay in the safe region. Instead of using the on-board
dynamic load circuit, an electric load can also be used
for the load step test, which does not have the 2%
maximum duty cycle limit for the load step.
3. It is recommended to set the electronic load in CR (con-
stant resistance) mode for evaluation of the DC2543B
board. Some electronic loads draw negative current in
CC (constant current) mode when evaluating the output
overcurrent protection feature of DC2543B, which can
violate the absolute maximum voltage rating –0.3V for
V
LOW
pin.
