QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 473
HIGH EFFICIENCY DUAL OUTPUT POWER SUPPLY
LTC1702A
DESCRIPTION
Demonstration circuit 473A is a high
efficiency dual output synchronous
buck converter using the constant
frequency LTC1702A dual channel
switching controller. It operates
from a 3V to 7V input and generates
1.8V at 5A and 2.5V at 5A. The
LTC1702A operates at 550kHz typical
switching frequency and uses voltage
mode control to switch a pair of N
channel MOSFETs. MOSFET R
DS(ON)
is
used for short circuit protection.
For operation at 3.3V, the demo board
uses sub-logic level power MOSFETs.
Design files for this circuit board
are available. Call the LTC factory.
QUICK START PROCEDURE
Demonstration circuit 473 is easy to
set up to evaluate the performance of
the LTC1702A. Refer to Figure 1 for
proper measurement equipment setup
and follow the procedure below:
NOTE:
When measuring the input or
output voltage ripple, care must be
taken to avoid a long ground lead on
the oscilloscope probe. Measure the
input or output voltage ripple by
touching the probe tip directly
across the Vin or Vout and GND termi-
nals. See Figure 2 for proper scope
probe technique.
1.
Place jumper JP1 in the CONT posi-
tion.
2.
With power off, connect the input
power supply to Vin and GND.
3.
Turn on the power at the input.
NOTE:
Make sure the voltage will
not exceed 7V at turn on.
4.
Check for proper output voltages.
Vout1 = 1.764V to 1.836V, Vout2 =
2.450V to 2.550V
In case of no output, verify that
the load is not set too high by
temporarily disconnecting the load.
5.
Once outputs are established at the
proper voltages, adjust the loads
within the operating range and ob-
serve the output voltage regula-
tion, ripple voltage, efficiency
and other parameters.
See Figure 3 to Figure 7 for ex-
pected performance.
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