4
dc2468af
DEMO MANUAL DC2468A
IN_EMI
QUICK START PROCEDURE
Demonstration circuit 2468A is easy to set up to evalu-
ate the performance of the LT8645S. Refer to Figure 5
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 output voltage ripple by
touching the probe tip directly across the output capaci-
tor. See Figure 6 for the proper scope technique. Figure 7
shows the output voltage ripple measured at the output
capacitor C9.
1. Place JP1 on BURST position.
2. With power off, connect the input power supply to
VEMI and GND. If the input EMI filter is not desired,
connect the input power supply to VIN and GND.
3. With power off, connect the load from VOUT to GND.
4. Turn on the power at the input.
NOTE: Make sure that the input voltage does not
exceed 65V.
5. Check for the proper output voltage (V
OUT
= 5V).
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high or
is shorted.
6. Once the proper output voltage is established, adjust
the load within the operating ranges and observe the
output voltage regulation, ripple voltage, efficiency and
other parameters.
7. An external clock can be added to the SYNC terminal
when SYNC function is used (JP1 on the SYNC posi-
tion). Please make sure that R2 should be chose to set
the LT8645S switching frequency equal to or below the
lowest SYNC frequency. JP1 can also set LT8645S in
spread spectrum mode (JP1 on the SPREAD-SPEC-
TRUM position) or pulse skipping mode (JP1 on the
PULSE-SKIPPING position).
Figure 5. Proper Measurement Equipment Setup
