Quick Start Procedure - Linear Technology DC2253A Demo Manual

DEMO MANUAL DC2253A

Quick start proceDure

Demonstration circuit 2253A is easy to set up to evaluate
the performance of the LTC3789EGN. 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
(6V to 36V) and GND (input return).
2. Connect the 12V output load between V
(Initial load: no load).
3. Connect the DVMs to the input and output. Set the
default jumper position, JP1: ON.
4. Turn on the input power supply and check for the proper
output voltages. V
OUT
5. Once the proper output voltages are established, ad-
just the loads within the operating range and observe
the output voltage regulation, ripple voltage and other
parameters.
Note: When measuring the output or input voltage ripple,
do not use the long ground lead on the oscilloscope probe.
See Figure 2 for the proper scope probe technique. 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
and GND
OUT
should be 12V ±2%.
Optional Master-Slave Paralleling Scheme
Besides the default paralleling scheme by tying the I
together, another optional Master-Slave scheme can be
achieved on the demo board to obtain a better sharing of
the inductor currents and output currents between phases.
IN
Please refer to the schematic in Page 8. To implement it,
1. Remove R67, R69 and R70.
2. Populate R68, R71 with 0Ω.
3. Set R 5~10% higher than R
FB3
4. Choose the current reference divider R65 and R66 so
that when the Vout is regulated, the voltage drop on
R65 is equal to V
limit threshold voltage. For example, when I
grounded, V
ILIM
= 100Ω and R66 = 24kΩ and then the voltage drop on
R65 will be 50mV.
and set R
FB1
, where V is the output current
ILIM ILIM
= 50mV. For V = 12V, select R65
OUT
pins
TH
= R .
FB4 FB2
pin is
LIM
dc2253af