TPS23861: PSE_N2 output of TPS23861 is abnormal

Jerry Hsueh

Part Number: TPS23861

Hi TI

The PSE_N2 output of TPS23861 is abnormal and will jump between 27V and 45V (the voltage should be 0V after the POE device is required).

We have the following checks:

1. Output is normal 48V.

2. CH2_GATE Voltage is 0V

3. SHUTDWN_N Voltage is 3.2V

Can you check the reason for the abnormal output of PSE_N2?

Thank you,

Jerry

over 6 years ago

0 Aidan Davidson1 over 6 years ago

TI__Intellectual 2640 points

Hi Jerry!

It sounds like your TPS23861 is still looking for a PD and is presenting an Open Circuit Detection waveform.

For a related E2E question, take a look here --> https://e2e.ti.com/support/power-management/f/196/p/808156/2991392?tisearch=e2e-sitesearch&keymatch=tps23861#2991392

The TPS23861 datasheet can be downloaded from this link --> http://www.ti.com/product/TPS23861

To avoid Open Circuit Detection, turn off detection for that channel.

Thank you for reaching out to us today and let us know if you have any more questions!

Aidan Davidson

0 Aidan Davidson1 over 6 years ago in reply to Aidan Davidson1

TI__Intellectual 2640 points

Hi Jerry!

What do you mean by (the voltage should be 0V after the POE device is required)?

The voltage jumping between 27V and 45V on PSE_N2 is expected behavior when the TPS23861 is reading an open circuit on a port. If there is a point during your device's operation where the TPS23861 is no longer needed, then the best course of action would be to set that the ports to OFF mode. More information on how to do that can be found in Section 7.4 of the TPS23861 datasheet. Disabling detection will also prevent the Open Circuit Detection waveform, but no further PDs will be detected when they are connected to the port.

Thank you!

Aidan Davidson

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TPS23861: PSE_N2 output of TPS23861 is abnormal