TPS23753A: the POE OUTPUT is oV

user6217259

Part Number: TPS23753A

Hi ,
As a freshman,i copied from the 12V/1A demo as the attachment 1 and the attachment 2 is my design.I have a problem about the output of TPS23753A ,i have test as following:

1. Add DC24V at poeout+ and poeout- ,can get a dc12V at D26.

2. Add a Non-standard PSE equipment ---output DC48V/0.45A , also can get a dc12V at D26.

3.Add a standard PSE equipment--such as TP-POE150S,this one can support class0-3,IEEE802.3af. There's no single at D26 ,Then the POEOUT+ and POEOUT- has no voltage，maybe it disabled detect the PD。

How can i do to get a steady voltage？It confused me several days。

this attachment is the one i referenced

my design diagram，i cant get any voltage at D26 when use a PSE 。

over 5 years ago

0 Michael Pahl over 5 years ago

TI__Mastermind 21320 points

Hello,

Thank you for your question. I did a quick review of the schematic and it looks good. Since the design is working when power is directly applied, my thinking is to check the detection first.

Can you capture VDD-VSS, and separately VSS-RTN when you apply the PSE? This should show me if we pass detection / classification, and if the switching FET is turned on.

Thank you!

Regards,

Michael Pahl

0 user6217259 over 5 years ago in reply to Michael Pahl

Prodigy 30 points

hi,

Michael Pahl

Thanks for your reply.

The pictures are as following ：I choose the DC coupling way , and the Bandwidth limitations is closed at 60MHZ ,the oscilloscope probe I use one multiple,

The VDD-VSS ：

The VDD-RTN :

0 user6217259 over 5 years ago in reply to Michael Pahl

Prodigy 30 points

hi，

Michael Pahl，

Thanks for your reply。

I add these two pictures ，I use the DC coupling，the bandwith is closed at 60MHz，the Oscilloscope probe is multply one。

The VDD-VSS ：

The VDD-RTN：

0 Michael Pahl over 5 years ago in reply to user6217259

TI__Mastermind 21320 points

Hello,

Thank you for the scope shots. Can you provide the schematic for the front end?

Also, do you have an EVM with you?

Regards,

Michael Pahl

0 Michael Pahl over 5 years ago in reply to Michael Pahl

TI__Mastermind 21320 points

Hello,

We have not heard anything from you end in almost a week. I will consider this thread solved if I do not hear from you in 48 hours. You are always welcome to post here if the issue is on going, or create a new post if a new issue arises.

Thank you for your interest in TI PoE products.

Regards,

Michael Pahl

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TPS23753A: the POE OUTPUT is oV