The form did not accept the TI p/n for some reason. We’re experiencing a repeating problem on a new design. I have attached a schematic
The design uses two (U38 & U57) load switches (TPS22920YZPR) from TI, they share a common enable. Each switch supplies 3.3V to two QSFP cages. The cages are empty. The only DC load is the recently added 332 ohm bleeder resistor.
We have had several U38 & U57 fatalities. We thought we found and fixed the problem. The 3.3V input would ramp down quickly. The unloaded (cages are empty) output bulk caps discharged back through the body diode of the pass FET to the power input pin and the enable input pin. We added bleeder resistors to the output and confirmed the output ramped down faster than the input – so the body diode wasn’t conducting anymore at power off.
We added the bleeder resistors and changed U38 & U57 in case the ICs had been stressed by repeated power cycles. Well, the new U57 now dies after being powered up for a couple of minutes.
Here’s a snippet of schematic. U38 & U57 circuits are identical. The VSW_SYS_3V3 input rail has 100’s of uF in bulk decoupling.TPS22920YZPR.pdf