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dc1860bfa
DEMO MANUAL DC1860B
qUick stArt proceDUre
Demo circuit 1860B is easy to set up to evaluate the
performance of the LT3748. Refer to Figure 1 for proper
equipment setup and follow the procedure below.
1. With power off, connect the input power supply to the
board through V
IN
(E1) and GND (E2) terminals.
2. Connect the load to the terminals V
OUT
+
(E6) and V
OUT
–
(E7) on the board.
3. Turn on the power at the input. Increase V
IN
slowly to
10V.
NOTE: Make sure that the input voltage does not exceed
15V. If higher operating voltage is required, power com-
ponents with higher voltage ratings should be used.
4. Check for the proper output voltages. The output should
be regulated at 52.5V (±5%).
NOTE: The LT3748 requires minimum load to maintain
good output voltage regulation. A zener diode D1 together
with preload resistors R2, R14, R15 and R16 are placed in
the output to clamp the output voltage to ~52.5V without
ex-board preload requirement. The efficiency is higher
than 90% without the preload resistors, but the output
may exceed 57V under no load or transient condition.
5. Once the proper output voltage is established, adjust
the input voltage and load current 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
terminals of the input or output capacitor. See Figure 2 for
proper scope probe technique.
NOTE: A gate resistor of less than 10Ω can be added
to the demo circuit to slow down the turning off of the
switch, and reduce the switching node voltage spike. A
RC snubber can be added as well to the primary winding
of the transformer to damp the spike and reduce the EMI.
