TPS23753A: TPS23753APW

Brijesh Kathavadiya

Part Number: TPS23753A

Tool/software:

Hello TI Team,

We are failing into conducted emission test for the 24VAC input path, while it is passing with POE path. Below is the circuit diagram of both the path with PD controller.

This is TI EVK SCH

We have tried to implement same circuit of 24VAC from TI EVK SCH but have used some different components.

The CMC used in our circuit is ACM4520-142-2P-T000, While in TI EVK it is P0420NL. Do you think that our CMC will not work here for the CE?

Can you please suggest us solution to pass the CE?

Thank you,

Brijesh K

6 months ago

0 Diang Xing 6 months ago

TI__Mastermind 37061 points

Hi Brijesh,

PoE team is doing internal tests and the reply on E2E may be delayed for 3 - 5 business days. Sorry for the delay and thanks for your patience.

Best regards,

Diang

0 Brijesh Kathavadiya 6 months ago in reply to Diang Xing

Prodigy 30 points

Hi Diang,

Thank you for your reply,

So TI EVK has been not CE tested ?

I would request you to please suggest solution quickly because we have release PCB gerber files to customer after passing the CE test.

Thank you,

Brijesh K

0 Diang Xing 6 months ago in reply to Brijesh Kathavadiya

TI__Mastermind 37061 points

Hi Brijesh,

Thanks for your patience. Most of PoE EVM does not go through EMI test. There could be one/two ran the EMI and have the results in application note.

Designing an EMI Compliant PoE with Isolated Flyback: www.ti.com/.../slua469.pdf

Best regards,

Diang

0 Brijesh Kathavadiya 6 months ago in reply to Diang Xing

Prodigy 30 points

Hi Diang,

The app note you shared does not have CE test details with 24VAC input section because we are failing on the 24VAC input but not on POE input, on POE input our CE is already passed.

in TI EVK CE is not tested with 24VAC input?

Please help me how we can pass CE on 24VAC input?

Thank you

Brijesh K

0 Brijesh Kathavadiya 6 months ago in reply to Brijesh Kathavadiya

Prodigy 30 points

Hi Diang,

we have also performed the CE testing with POE input and in that as well we are failing on the High frequency side.

We have tested 3 different devices with POE input but they are having same POE circuit which is shared as below. In all 3 devices we are failing on the High frequency side, Graphs of all 3 devices are attached please check and can you please let me know what can be reason for the failure and what can be the solution?

CE_Issue.zip

0 Diang Xing 6 months ago in reply to Brijesh Kathavadiya

TI__Mastermind 37061 points

Hi Brijesh,

Solder the these two decoupling capacitors to compensate the switching transient.

Considering the Q1 is a very small die FET with 700mOhm on resistance, you can further increase the R14 to 100 Ohm. It is also optional to add the snubber R17 and C37. Or you may consider using a FET with 100 - 200 mOhm on resistance.

If above changes do not help, you can consider to further add Y-caps.

Best regards,

Diang

0 Brijesh Kathavadiya 5 months ago in reply to Diang Xing

Prodigy 30 points

Hi Diang,

We have done all the suggested reworks into POE section and below are results so can you please check and suggest us what we can do further?

0 Diang Xing 5 months ago in reply to Brijesh Kathavadiya

TI__Mastermind 37061 points

Hi Brijesh,

Thanks for your updates. I will look through and get back to you in 3-7 business days.

Best regards,

Diang

0 Brijesh Kathavadiya 5 months ago

Prodigy 30 points

Urgent !

Hi Diang,

Can you please suggest me solution for this 24VAC circuit, how we can solve the conducted emission ? Can you please suggest me modification required in 24VAC circuit?

This is stuck since long time and we have not heard from you for this 24VAC we have to solve it urgently

Thank you

Brijesh K

0 Diang Xing 5 months ago in reply to Brijesh Kathavadiya

TI__Mastermind 37061 points

Hi Brijesh,

Can you let me know which MOSFET at Q1 you are using now?

If the issue only happens with 24VAC case? It means your voltage at adapter after rectifier is 24V * sqrt(2) = ~34V?

You may try change R16 to 50k or 75k to set fsw = 200k or 300k see if get better results

Check below link for more information

https://www.ti.com/lit/an/slua469/slua469.pdf

Best regards,

Diang

0 Brijesh Kathavadiya 5 months ago in reply to Diang Xing

Prodigy 30 points

Hi Diang,

We are using AM3490N-T1-PF Mosfet. The conducted emission failure happens with both the input cases (with 24VAC Input & POE Input as well).

0 Diang Xing 5 months ago in reply to Brijesh Kathavadiya

TI__Mastermind 37061 points

Hi Brijesh,

Thanks for your reply.

Could you share the datasheet of AM3490N-T1-PF if it is not as below?

As we discussed the Q1 is a very small die FET with 700mOhm on resistance, you can further increase the R14 to 100 Ohm. It is also optional to add the snubber R17 and C37. You better consider using a FET with 100 - 200 mOhm on resistance. Especially you have 24V * sqrt(2) = ~34V input which is lower than common PoE 37-57 Vin and with higher current.

Best regards,

Diang

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TPS23753A: TPS23753APW