TPS2379: TPS2379

Rock Shao

Part Number: TPS2379
Other Parts Discussed in Thread: TPS2373

Test according to the following circuit diagram, the probe is connected before the rectifier bridge.
The load is two parallel 194ohm non-inductive resistors, the load power is about 30W,
the input is connected to the PoE switch network port, and the IC uses TI’s TPS2379.

The LED on the load board flashes once, but the load board does not work normally. Every time, the LED on the load board flashes once.
The previous conditions remain unchanged, one of the back loads is disconnected, that is, the load power is 15W, and the load board can work normally

Please help confirm what is causing the problem.

Thanks and regards
Rock

over 2 years ago

0 Michael Pahl over 2 years ago

TI__Mastermind 21320 points

Hello Rock,

The TPS2379 is a IEEE802.3.at device. The maximum power a IEEE802.3.at PSE can provide is 30W at the output of the PSE -- which is 25W at the input of the TPS2379 because of power loss in the cable.

Then there is further power loss in the power rectification and the DCDC, so the load cannot even be 25W.

The issue is the PSE is shutting off power. Try a high power PSE and changing the class resistor to negotiate higher power. you already confirmed it is not our device since it successfully negotiates power at 15W load. Thanks

If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

Regards,

Michael P.

Applications Engineer

Texas Instruments

0 Rock Shao over 2 years ago in reply to Michael Pahl

Expert 2860 points

Hi Micheal,

If I want the 30W output, do I need to change to the IEEE802.3.bt IC device?
Did you have any suggestions? thanks.

0 Michael Pahl over 2 years ago in reply to Rock Shao

TI__Mastermind 21320 points

Hello,

Yes, if you need 30W at the output, then it will require both a ieee802.3.bt compliant PD and PSE.

I'd suggest the TPS2372-3. This device is a standalone PD like the TPS2379, but it integrates the pass MOSFET. It does not have an adapter pin or advanced startup (for downstream DCDC converters), so you can save on cost over the TPS2373.