TPS2378: TPS2378 problem

Hello,

If you are using the schematic above, there is no power stage. There is no DC-DC conversion, so it makes sense that the full 48 is passed to the PD. 

If you want a different voltage, design a buck or flyback converter such as:  

IEEE802.3 standard requires that the PD send an MPS signal (maintain pulse signature). It requires 10mA be drawn from the PD. If there is no load, this signal is probably not being done, so the PSE is shutting down power. Then the PD and PSE reset and do another detection. 

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

Regards, 

Michael P.

Applications Engineer

Texas Instruments 

Hi,

I have supplied LM5088 DC DC regulator with output of TPS2378 and the result was same. At start up LM5088 output turned on and after 500ms it turned off again. Could this be related to the my RJ45 connector? Because i have noticed that it is 802.03af RJ45, but TPS2378 is 802.03at, i am not sure, any advise ?

Thanks...

Hello,

Did the DC-Dc have a load on it? Most DC-DCs will not draw more than 10mA when it does not have any load on it. 

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

Regards, 

Michael P.

Applications Engineer

Texas Instruments 

Hi,

DC DC has 24V output and it has 250mA load on its output.

Hi

I have connected a 100nF bias capacitor but it didn't work again. When i supplied LM5088 with any power supply, LM5088 circuit works, but it does not work with TPS2378.