This was entered as a follow up question on my original post. I guess the other was marked as closed.
This is the LGA-18 package so inspecting the connections isn’t really possible. I suspect that the liquid may have been due to the cleaning process at the assembler. I didn’t realize that the pin one indicator is actually a hole in the top metal cover. I am concerned that the can filling up with some solution may have caused an issue.
Some additional questions,
1 - I have a pullup on the power good circuit and a review of the data sheet leads me to believe that isn’t necessary. The internal diagram shows a pull to the internal VCC. I removed that resistor but didn’t see any change in the behavior.
2- As I stated, I’m concerned that some liquid got under the cap during cleaning. Are there any special instructions for assembly for this part? Should the hole be covered to avoid this?
3 - I’ve attached an image of the PCB top layer. It matches the recommendations pretty closely. Do you see any issues?
4 - I measured the output voltage on a scope and I see it start to rise quickly until it gets to about 3V then it ramps down more slowly to a level before rising quickly again. This resembles a sawtooth. It almost looks like the circuit is going into a thermal shutdown, cooling off and then restarting. I’m not feeling any heat on the cap. Does that provide any clues?
5- This supply acts as a pre-voltage stage for other supplies on the board. There are twelve CUI PDSE1-S5-S9-M 1W supplies that use the output of the 5V. There isn’t any way of disabling these supplies and bringing them up slowly but they only have a small load in the current configuration. Could this be causing an issue?
6 - I’ve submitted a request for a call. Hopefully that happens soon. We are also getting evaluation boards so we have something to compare with.
