DP83TC813R-Q1: Caps Required for Transformer Isolated 100BaseT1 PHY?

Velin Dimitrov

Hi,

I am interested in using the DP83TC813R-Q1 with a Wurth STST transformer and CNSW common mode line filter for a 100BaseT1 application in a high noise environment.

Wurth STST 74930000 (https://www.we-online.com/components/products/datasheet/74930000.pdf)

Wurth WE-CNSW 7442335900 (https://www.we-online.com/components/products/datasheet/7442335900.pdf)

The datasheet and checklist for the DP83TC813R-Q1 indicates that the cap coupling is required in all cases. I am assuming that even if I use the transformer, I need to add the caps so there isn't a short at DC across the transformer winding or will the PHY not be affected by that?

Thank you!

6 days ago

+1 Charles 6 days ago

TI__Expert 8713 points

Hi Velin,

I'll have a response by end of day tomorrow.

Best,

Charles

0 Charles 5 days ago in reply to Charles

TI__Expert 8713 points

Hi Velin,

For automotive application, AC capacitor is used for DC isolation. This is why we require this in the checklist.

The transformer by nature is galvanically isolated. AC coupling caps are not needed if transformer is used.

TI has an evaluation module for industrial applications using the Wurth components you mention above. This module has passed IEC 61000-4 tests for radiated and conducted noise: https://www.ti.com/tool/DP83TC812-IND-SPE-EVM

You can read more about SPE in industrial/robotics in this white paper: https://www.ti.com/lit/an/snla420a/snla420a.pdf

Best,

Charles

0 Velin Dimitrov 2 days ago in reply to Charles

Prodigy 10 points

Thank you!

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DP83TC813R-Q1: Caps Required for Transformer Isolated 100BaseT1 PHY?