TPS23753A: PD off after start

Maksym Ka

Part Number: TPS23753A
Other Parts Discussed in Thread: TPS23753

I try to create PoE based on TPS23753A for my DIY project. I use http://www.ti.com/lit/an/slva305c/slva305c.pdf as start point.

I have 2 PSE - Netis PE6105 and WS-C3560-48PS.

With WS-C3560-48PS all ok, board start and works without issues.

With Netis PE6105 board start, provide 3.3 V output but turn off after ~ 1 second. After that it start again, off in 1 second and repeat.

I found strange behaviour - board able to start after preheating input circuit (bridge + tps23753) with hot air.

I can't understand this behaviour. Some china cameras works without issues on this switch.

What i should check to resolve issue?

over 6 years ago

0 Thomas Lewis over 6 years ago

TI__Expert 5615 points

Maksym,

I will assign this thread to an Applications Engineer for further guidance; however, I first want to make you aware of the PoE logo program that is intended to minimize situations like this moving forward. Through the EA, the industry is rolling out a PoE logo which will make it clear that a piece of end equipment (load or supply) has passed interoperability testing. I encourage you to consider this program for your own projects moving forward and to make any switch vendor offering a troubling model aware of it. You can learn more about the program via our E2E FAQ on the topic located here --> .

Our Application Engineer will follow up with you shortly to aid your efforts further.

Thank you for considering PoE products from Texas Instruments,

0 Darwin Fernandez over 6 years ago in reply to Thomas Lewis

TI__Mastermind 41800 points

Hi Maksym,

Can you try adding a load to your 3.3V output to see if the cycling goes away? It's probably MPS as described in the datasheet. Thanks!

0 Maksym Ka over 6 years ago in reply to Darwin Fernandez

Prodigy 40 points

Loading didn't change nothing. You can see below behavior with 1A load (3.3 Om resistor):

CH1 (yellow): GATE pin

CH2 (blue): VDD

All measurements related to RTN pin.

Start and stop with PSE SW-1:

With another PSE all works:

0 Maksym Ka over 6 years ago in reply to Maksym Ka

Prodigy 40 points

I try to understand who break power - TPS23753 or PSE.

I measured levels on VSS and RTS pin related to VDD. It looks like PSE power off PD.

CH1 - VSS

CH2 - RTN

Start:

stop:

0 Maksym Ka over 6 years ago in reply to Maksym Ka

Prodigy 40 points

CH1 - Vdd

CH2 - RTN

Related to Vss

0 Darwin Fernandez over 6 years ago in reply to Maksym Ka

TI__Mastermind 41800 points

Hi Maksym,

Can you forward your schematic so we can review it? At first glance looking at your waveforms, the gate looks like it is pulse skipping and it could be that the current is low enough from the PSE prospective to remove power.

Also have you tried ordering a TPS2753AEVM-004 just to see how it behaves with that specific PSE?

Lastly the waveform helps slightly but can you take something similar to figure 16 of the TPS23753A datasheet (in DC coupling and not AC)? Thanks!

Power management

Power management forum

TPS23753A: PD off after start