Part Number: TPS55289
Setup: Two TPS55289 channels on one shared I2C bus (different addresses via MODE strap, 0x74/0x75). VIN = 12V.
Issue:
- Channels 1 and 2 stopped responding on I2C. Shortly after, the shared bus (both SDA and SCL) latched permanently low.
- Channel 1 was physically removed from the board.
- The TPS on CH2 was removed and reinstalled (0x75 as attached) failed and are pulling the bus LOW: output stuck at 22.2V (seems to be running in OL (?)) and won't turn off, since we are unable to write to the IIC bus.
- VCC internal on the new part reads a healthy 5.2V. Bus is still stuck low (both SDA and SCL) even with the new chip in.
-Removing the TPS from the board fixes the IIC lines and they are all acting fine. I am using 5.2K pull-up resistors.
Questions:
1. What could cause a TPS55289 to internally clamp SDA/SCL low? Any known failure mode for this?
2. Bus is still low after a full chip swap on channel 2. I have multiple factory-assembled boards, and all of them seem to be showing the same issues (SDA/SCL pulled LOW).
3. Any recommended way to isolate a bus lockup like this to a specific device vs. a board-level short?
Trying to figure out if this is a chip-level failure mode or a board assembly issue before doing another swap.
