Hi
During production our factory reported several broken USB-Ports on their testing machines. Upon investigation, we realized that a few units had faulty TPS65987DDHRSHR where the connection between PP_HV1 (where our 20V Power Supply is connected to) and VBUS1 (where the testing machines where connected to) was faulty (= 0.78 Ohms resistance in both directions, even when unpowered or TPS-configuration deleted from flash). This caused the 20V from the PSU being forwarded to the connected USB-Ports on the host testing machines and destroying those ports.
We have not figured out the cause for the TPS65987DDHRSHR breaking in this way and also could not reproduce it so far. Based on the already produced volume and testing we did, we estimate that about 0.1% - 0.05% of the produced units had TPS65987DDHRSHRs showing this fault.
Question:
We plan to put a diode (short term: rework of already produced units) or an ideal diode (long term: with PCB layout change) in the VBUS1 power-path to block the potential 20V from destroying connected USB devices if such a failure should happen again. Would you also recommend this? (it somehow sounds silly to put a diode in front of another diode because we had experienced a few issues with it...)
Hope to get some help soon!
Thanks in advance,
Mark
