Hi all!
have a buck regulator based on TPS5430 from TI, which wouldn't start properly. The design has been done using TI WEBENCH tool & all the components have been chosen from the recommended BoM. However, when I supply 12V in, the output voltage gets stuck at 1.255 V and the PH pin scope trace just shows weird oscillations. What is also weird, the Vsense pin also shows 1.255V, while according to the datasheet it should be 1.221V (internal REF).
I tried playing with input/output capacitance - no luck. Again, the input and output caps were chosen according to WEBENCH recommendations. What I've found is that if I briefly short the bootstrap capacitor, the circuit would start, though the PH trace still looks weird on the scope. If I switch it down and let Cout fully discharge, it wouldn't start again without kicking Cboot.
Now, the datasheet explicitly says to use Cboot of 10n, which is exactly what I've done. I've tried 4.7n and 2x10n in parallel instead - that didn't help.
Any ideas what the reason could be?
