MP9486A Vin range issues

DC-DC Power Converters
#1

I followed the eval board circuit/layout exactly. I have a really hard time getting it to start up with any sort of load on it (>=100ma) with Vin < 11 volts. Over 11v Vin and everything is fine.

At first it wouldn’t start up at all with load attached regardless of Vin, until I removed the tantalum 100uF Cout and replaced it with a 100nF ceramic (maybe it’s too much with 100uF already in the load). At <11v Vin, I can start it with no load and then attach the load, but regulation is not good at all.

Does anyone have any suggestion to get this to work better in the 10-11v Vin range?

#2

Hi,
Thank you for utilizing MPS Technical Forum.

Can you please check for the following:

  1. Do you have enable pin floating?
  2. can you please check the feedback network, and possible misconnections on the board?
  3. Might have to try a slightly larger cap to and previous step to help with proper regulation.
  4. what are your output specs?

Regards,
Nouman

#3
  1. Yes, it is floating (tied to DIM)
  2. I checked it, feedback is good
  3. If I increase Cout more than 50uF, it will not start at all at <11v Vin
  4. 5V output, 300mA maximum load