TPS23880: Connecting DRAINn to GND

Kevin Lai

Part Number: TPS23880

Hi team,

my customer is concerned about the phrasing in the datasheet which states "If the port n is not used, DRAINn can be left floating or tied to GND."

does this mean you must leave the output unconnected from any load?

there is also an internal resistor between VPWR and GND of ~100k. will there be ~500uA of leakage here for the unused port?

Thanks,

Kevin

over 5 years ago

0 Penny Xu over 5 years ago

TI__Genius 15685 points

Hi Kevin,

Yes. If you connect the drain pin to ground, there would be power loss. So it is better to leave the drain pin open if the channel is not used. Thanks.

Best regards,

Penny

0 Kevin Lai over 5 years ago in reply to Penny Xu

TI__Intellectual 2916 points

Penny,

Thanks for that info. But i still need answers for the rest of my question. It appears tying the drain to GND could be catastrophic beyond power loss. Please see the note I attached to this threads submission. Should someone plug in a non POE PD, the PD will be subjected to the full PS voltage and destroy the downstream circuits. Please help address this issue/current understanding. The data sheet says you can connect to GND which would be dangerous in this example.

Thanks,

Kevin

0 Penny Xu over 5 years ago in reply to Kevin Lai

TI__Genius 15685 points

Kevin,

If the port is unused, there's no connection between PSE port to the RJ45. Why would it matter if you connect a non PoE PD to the port with only data connection? Thanks.

Best regards,

Penny

0 Kevin Lai over 5 years ago in reply to Penny Xu

TI__Intellectual 2916 points

Perfect thanks Penny!

Power management

Power management forum

TPS23880: Connecting DRAINn to GND