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TPS53679: Device not detecting on PMBUS and incorrect VREF

Part Number: TPS53679
Other Parts Discussed in Thread: UCD90160, TPS536C7

Hello

We are using TPS53679 power controller device. We applied 3.3V (no 5V and 12V) but TPS53679 device is not detected by TI USB dongle. There are 2 TPS53679 devices, 1 UCD90160 and 1 TPS536C7 device on the same PMBUS. TPS536C7 and UCD90160 devices are detected. But none of the TPS53679 is detected.

Few observations regarding this:

  1. After applying 3.3V, VREF voltage is 1.55V (pin 1)[for both TPS53679]
  2. After that 5V is turned on for power stage. Now VREF = 2.3V (for first device) and 1.85V(for 2nd device)

Expected VREF as per datasheet is 1.7V. Please let us know possible causes for this issue.

Regards

Kunal