Other Parts Discussed in Thread: TPS23861, TPS2388
Dear Sir :
I attached circuit for TPS23754 POE design ,
please help to check if it is correct or not,
thks.
Best Regards,
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Hi Arang,
Thanks for your questions. Here are my comments.
1. The Bob Smith termination is wrong. It should be like this. The 0.01uF cap is necessary.
2. The clamp FET is wrong. It should be PFET instead of NFET.
3. Output cap is too large. Usually 100uF bulk cap plus several ceramic 10uF cap are enough.
4. It is recommended to add another 2.2uF cap on the primary side input. Beside C3005.
5. D3007 and D3011 should be uni-directional diode because the PD controller can't handle negative voltage. The EVM I attached below is a good reference for you.
I don't have transformer information, but usually the primary inductance should be about 100uH.
Here are two 12V class 4 PoE design for your reference.
Thank you.
Best Regards
Jack Chen
0207.POE.pdfHi,
update modified POE circuit in attached file,
please help to check it.
thks.
Best Regards,
Arang
Hi Arang,
Since this is a type 2 PD, you should use type 2 PSE supporting at standard like our TPS23861 or TPS2388.
Thank you.
Hi Jack,
Thinks for your support. This is Taiwan FAM Jin Lin
Could you help to reply my customer's question.
Is there any side effect if they still use 0.1uF (C3029~C3032) connect to GND?
Jin
Hi Jin,
C3029-C3032 effects the data path so the power will be unaffected. The termination of the center taps of the data transformer are dependent on the PHY that is used on the data side. Its datasheet will typically say how this should be terminated.
Thanks!