Hi, I am bringing up a board with multiple MPM3683-7 DC-DC converters.
One of them worked at first, and the other two either had a low VOUT (around 0.6V) or VOUT = 0V.
Now all three do not work.
Attached is my schematic and layout. I had originally connected the 4.7nF capacitor between GND and SENSE+ rather than VOUT and SENSE+ - this is now fixed, but yet they still do not work.
Could this have permanently damaged the modules somehow? Is there anything else that I should try before potentially breaking another board?
VIN = 12V (this has never been exceeded)
RAIL_PG is not being pulled low on any chip
RAIL_PG is not connected anywhere else
VCC seems to be 1.2V, 2.0V, and 0V on the three chips (the only difference is the one resistor between VO_SENSE+ and GND, everything else is identical)
EN pin is at 4.3V, 4.3V, and 11V respectively on the three chips
VO_SENSE+ pin is at 0.20. 0.28, 0.0V respectively
12V rail is at 12.0V, drawing <20mA.
When the board was first powered on, it drew >300mA for a short while and then now draws only <2mA - perhaps something has blown up inside the chips? It is unclear what the issue would be
Applying external 3.3V to the VCC pin, the pin draws 70mA, and the output voltage goes up slightly, but not enough (from 0.4V to 0.8V rather than the target 1.8V)
I have checked all the resistor values. I suspect the parts have all broken/blown up but I cannot figure out what would have caused it and I only have one other board I can try…
