TMUXHS4212: RX ac cap with MUX

Fred Cheng

Expert 5790 points

Part Number: TMUXHS4212

HI David,

I know you've taught us this last time, but the memory is kind of vague now.

if customer want to add ac cap at RX to further protect ESD, I know the Ac cap value should be 0.33uF.

but where should we add the bias pull up?

over 1 year ago

0 David (ASIC) Liu over 1 year ago

TI__Guru**** 178006 points

Hi,

It is correct that for RX, the optional cap is 0.33uF.

But if there is no AC coupling cap between the host and the TMUXHS4212, then the host TX and RX will bias the MUX as long as the host bias voltage meets the MUX bias voltage requirement.

If the host bias voltage does not meet the MUX bias voltage requirement, then you will need to AC couple between the host and the TMUXHS4212. And the external bias network need to be added between the AC caps and TMUXHS4212 and can be done at either side of the MUX. This external bias network has to meet the MUX bias voltage requirement.

Thanks

David

0 Fred Cheng over 1 year ago in reply to David (ASIC) Liu

TI__Expert 5790 points

Hi David,

so first I need to check the bias voltage of the Realtek USB hub, if the voltage meet the spec of our mux,

then we can just add those RX 0.33uF between Mux and connector, right?

0 David (ASIC) Liu over 1 year ago in reply to Fred Cheng

TI__Guru**** 178006 points

Fred

Yes, but the 0.33uF is optional.

Thanks

David

0 Fred Cheng over 1 year ago in reply to David (ASIC) Liu

TI__Expert 5790 points

Sorry one more thing to check ,

is common voltage the bias voltage you referred to?

I see our high speed common voltage range can tolerate 0~1.8V under 3.3VCC in our datasheet

+1 David (ASIC) Liu over 1 year ago in reply to Fred Cheng

TI__Guru**** 178006 points

Fred

Yes, common mode voltage is the same as bias voltage.

Thanks

David

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TMUXHS4212: RX ac cap with MUX