Other Parts Discussed in Thread: CSD18534KCS, LM5088
Tool/software:
Hi everyone!
I've designed a DC-DC converter based on the LM5088MH-2/NOPB Buck Controller, with the following specifications:
- Input (Vin): 36V DC
- Output (Vout): 32V DC
- Output Current: 1.5A
I used TI’s Webench tool for the initial design and referenced both the datasheet and evaluation boards for the layout. I've also made some modifications to meet my requirements:
- MOSFET: CSD18534KCS (TO-220-3 package)
- Cboot: 67nF
- Cout: 390uF + 22uF + 10uF + 0.47uF
I’ve attached the schematic in the files:
When I powered up the board using an external power supply, I noticed that the output is stuck in hiccup mode, even with no load attached. The hiccup reset time is around ~928ms. Adding a small load doesn’t change the behavior—it's still in hiccup mode even after multiple power resets and attempts at debugging.
I have used restart capacitor of 2.2uF which gives 52.8ms for Trestart_delay.
Here’s what I’ve checked so far:
- Temperatures : all components are ~=31 degC
- Pin 16 (VCC) voltage: ~8V
- Pin 2 (EN) voltage: ~1.5V
- SS time: Increased to 10ms, but the issue persists.
- Switching frequency: Lowered to 126kHz, no improvement.
Additionally, after a while, I hear an audible ticking sound from the inductor. I swapped the inductor, but the issue remains.
I've also attached the Vout oscilloscope graphs showing the behavior.
Any help or insights would be greatly appreciated! Thanks!
