Linear Technology DC1694B Demo Manual page 2

DEMO MANUAL DC1694B
QUICK START PROCEDURE
Demo circuit 1694B is easy to set up to evaluate the
performance of the LT3748. Refer to Figure 1 for proper
measurement equipment setup and follow the procedure
below.
1. With power off, connect the input power supply to VIN
and GND.
2. Connect the load to the terminals VOUT+ and VOUT– on
the board. Apply a load between 100mA to 2.5A to the
output.
3. Turn on the power at the input. Increase VIN to 22V.
NOTE: Make sure that the input voltage does not exceed
75V.
4. Check for the proper output voltages. The output should
be regulated at 12V (±5%).
NOTE: If there is no output, temporarily disconnect
the power supply. Make sure that the load is properly
connected. If the output voltage is out of spec, make
sure minimum load current is applied to the output,
the load is not set too high, and the DC power supply
does not hit the current limit.
2
NOTE: If higher operating voltage is required, power
components with higher voltage ratings should be used.
NOTE: The LT3748 requires minimum load to maintain
good regulation. A Zener diode D4 is placed between
VOUT+ and VOUT– to clamp the output voltage to ~13V
if minimum load requirement is not met. Depending on
input voltage and output regulation, a 100mA minimum
load is usually sufficient.
5. Once the proper output voltage is established, adjust the
input and load within the operating range and observe
the output voltage regulation, ripple voltage, efficiency
and other parameters.
NOTE: When measuring the input or output voltage
ripples, 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 and GND, or VOUT+ and VOUT– terminals. See
Figure 2 for proper scope probe technique.
dc1694bfa