TPS23753 PoE circuit discussion

TT_Chin

Expert 2025 points

Other Parts Discussed in Thread: TPS23753, TPS23753AEVM-001

Hi Darwin,

We have discussed TPS23753 PoE circuit before.

I have a thermal event and need confirm it with you.

Please see attachment of schematic that I provided to you two months ago.

I found R195 (10Ω 1% 0805) is about 80 degree C when system run in 8 watt.

It is hot point. Is it okay for the resistor? I also found the other EVM use 49.9Ω, should I change the vale from 10Ω to 49.9Ω or other values?

Thanks for your help!

Sincerely,

Jefer

TPS23753_Layout.rar

TPS23753_schematic.pdf

over 7 years ago

0 TT_Chin over 7 years ago

Expert 2025 points

Hi Darwin,
I remove C257(1000pF 100V 0603) from schematic, the thermal issue of R195 disappeared.
Does C257 need to mount in schematic? What's the job function of C257? for switching noise reduction or other purpose?
I saw some EVM don't have this RC circuit.
Thanks!

Sincerely,
Jefer.

0 Darwin Fernandez over 7 years ago in reply to TT_Chin

TI__Mastermind 40100 points

Hi Jefer,

The series Vc resistor is used to reduce peak charging from the bias winding. Typically it'll go as high as 100 ohms. You can start with 10 ohms, if you find the voltage on VC is high, then you can increase the resistance.

C257 should not be installed here as I've not seen this implemented before.

Regards,
Darwin

0 TT_Chin over 7 years ago in reply to Darwin Fernandez

Expert 2025 points

Hi Darwin,
Okay, thanks!

Sincerely,
Jefer.

0 Davood Motlagh92 over 6 years ago in reply to TT_Chin

Prodigy 60 points

Hello Darwin,

I like to use this part for and IP application, can you please send me the DSN file of your working eval-board? Thanks

0 Darwin Fernandez over 6 years ago in reply to Davood Motlagh92

TI__Mastermind 40100 points

Hi Davood,

Please clarify what eval-board you're referring to. The design above is TT_Jefer's design.

0 Davood Motlagh92 over 6 years ago in reply to Darwin Fernandez

Prodigy 60 points

Hi Darwin,

Any eval board that you find best helps to decide. I like to use TPS23753 for an IP cam with 5 or 3.3 volt out with very low power, less than 10 watt (2-7 watt is the goal). Please send in both PDF and DSN. I need DSN for symbols if we go to Capture schematic.

Thanks

0 Darwin Fernandez over 6 years ago in reply to Davood Motlagh92

TI__Mastermind 40100 points

Hi Davood,

Please see TPS23753AEVM-001. This is 7W, 5V flyback design and is orderable in the TI estore. Thanks!

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TPS23753 PoE circuit discussion