I recently used a TPS60403 in combination with TPS73225/73233 to create a negative voltage rail for a small opam circuit. In total I need approx. 45 - 50 mA on the negative rail (see attached schematic picture).
Now, the TPS60403 seems not to be very complicate but in this specific schematic I am not able to make it run (in other circuits the tps60403 works in our lab) - obviously there is something wrong; but what. I also attached two scope pictures from Pin 3 and Pin 5 with strange curve form (in other applications I measure a square wave with 250 kHz at Pin 3/5).
In addition, here, the TPS is getting quite warm, so maybe there is something oscillating (which I cannot measure with the scope). The output voltage is in the range of -0,7 V. The capacitors are all C0805C105K4RACTU (ceramic X7R).
Maybe the TPS60403 is broken (I am wondering about the 55 kHz, but I am quite sure that I mounted the 250 kHz version and not TPS60402)... What do you guys think?