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TPS549D22: Can't assert TPS549D22 SMB_ALRT pin

Part Number: TPS549D22

Hi TI,

I can't assert SMB_ALRT pin. The following is my test command.

Test command:
  # Check write protect. 
  # 0x0: Enable writes to ALL commands
  i2cget -y 0 0x14 0x10
  -> 0x00

  i2cget -y 0 0x14 0x25 w
  -> 0x019a

  i2cset -y 0 0x14 0x25 0x0180 w

  # OPERATION Register, Turn on VOUT Margin High and Act On Fault
  i2cset -y 0 0x14 0x01 0xA8d

Then I measure SMB_ALRT pin, the pin always keep HIGH status.

Could you help to check our test flow and command.



    I do not see anything wrong with your programming sequence, and you should observe VOUT decreasing from 0.8V to 0.75V, but this programming sequence is not expected to trigger SMB_ALERT.  The 6.25% decrease in VOUT is not sufficient to trigger an Under Voltage event which would create an SMB_ALERT.  Further, the Under voltage Protection in the TPS549D22 tracks the active reference voltage whether it is set by VOUT_COMMAND, MARGIN_HIGH or MARGIN_LOW, so it is generally not possible to induce an Over Voltage or Under Voltage event by changing the output voltage through a PMBus comment.

    You can induce an under or over voltage event by coupling a higher or lower voltage to the RSP pin, or you can trigger a Communications, Memory, or Logic (CML) fault by writing out-of-range data, or attempting to write to an unsupported command.  Alternately, you could write 2 bytes of data to a Write Byte commend, triggering a PEC failure with the second byte of data.