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TPS23861: schematic questions

Part Number: TPS23861
Other Parts Discussed in Thread: TIDA-010046

Hi team,

Could you please answer below questions?

1. Is it ok to change SEN1 resistor 22.1 ohm to 22ohm?

2. Is it ok to connect RJ45 and Xfmr as below?

3. Basically, PD device has two diode bridge as below, correct?

4. What does it mean by "extreme" here? What kind of situation?

TIDA-010046 uses 10MQ100NTRPBF. What is the expected environment to choose this?

5. Same as No.4, Could you please explain how to choose DPnB and DPnA?

Best regards,


  • Hi team,

    Any response for customer's questions?

    Best regards,


  • Hi Hideki-san,

    Thank you for the reminder here, it seems the thread was closed or missed from my end. 

    1. The FW expects a value of 22.1ohm. Therefore I would recommend using 22.1ohm however, I would expect the solution to work with 22ohm but can not gaurentee.

    2. Yes, this is okay connection as this would be considered Alt-B connection. From the PD side, the PD is always wired for 4-pair connection, and the 2-pair connection is on the PSE side. Typically, when using 2-pair PSE the signal pair should be used, however there is no risk to using spare pair.

    3. This is correct. The PD is always configured for 4-pair PoE and therefore, when connecting from PSE it should not make difference on PD side whether signal pair or spare pair.

    4. Extreme surge currents would be similar to lightning surge applications where we would expect a large rush of current. More common would be short circuit scenarios. 10MQ100NTRPBF is used for common application to withstand up to 1A surge current in a short circuit.

    5. DPnA is recommended in all applications to protect the port during any surge condition and to protect the IC from higher than expected voltages. DPnB is used optionally in conditions where we would expect large surge currents. Again, the main applications where I have seen this used or applicable is in environments where lightning surge is a factor.  I am attaching APP note regarding lightning surge for more informations.