SMARC DC blocking capacitors 100nF shall be placed on the Module

Technical Support
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1

Are on the SMARC IMX95 the DC blocking capacitors 100nF placed on the Module for USB3 SS lines?

2

Hi, I’m the Toradex AI Assistant.

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Based on the SMARC specification, for USB3 SuperSpeed lines, the DC blocking capacitors placement varies by signal direction (1):

USB3 SuperSpeed DC Blocking Capacitor Placement

For USB3 (Port 3) SuperSpeed signals (1):

  • USB3_SSTX+ and USB3_SSTX- (Transmit Signal Differential Pairs): DC blocking capacitors 100nF shall be placed on the Module (1)
  • USB3_SSRX+ and USB3_SSRX- (Receive Signal Differential Pairs): DC blocking capacitors 100nF shall be placed on the Carrier (1)

The same pattern applies to USB2 SuperSpeed signals (1):

  • USB2_SSTX+ and USB2_SSTX-: DC blocking capacitors 100nF shall be placed on the Module (1)
  • USB2_SSRX+ and USB2_SSRX-: DC blocking capacitors 100nF shall be placed on the Carrier (1)

So to directly answer your question: Yes, for the USB3 SuperSpeed transmit lines (SSTX), the 100nF DC blocking capacitors are placed on the SMARC iMX95 Module (1). However, for the receive lines (SSRX), the capacitors are placed on the carrier board (1).

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3

Are they on the SSTX lines? “shall” is not “must”

4

Yes, according to the SMARC specification, the 100nF DC blocking capacitors are placed on the Module specifically for the SSTX (transmit) lines (1).

For USB3 SuperSpeed signals:

  • USB3_SSTX+ and USB3_SSTX- (Transmit Signal Differential Pairs): DC blocking capacitors 100nF shall be placed on the Module (1)
  • USB3_SSRX+ and USB3_SSRX- (Receive Signal Differential Pairs): DC blocking capacitors 100nF shall be placed on the Carrier (1)

So to confirm: Yes, the 100nF DC blocking capacitors are placed on the SMARC iMX95 Module for the SSTX (SuperSpeed transmit) lines (1).

Did you like my answer? :+1: :-1:

If I answered your question, please tick the “Solution” checkbox.

For follow-up questions to me, please use @ToradexAI in your post.

5

Why are DC blocking capacitors in the SSRX lines on SMARC Eval Board V1.1 ?

6

The SMARC iMX95 module has coupling capacitors on the USB SuperSpeed TX lanes and no capacitors on the RX lanes.

To follow USB SS spec.

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7

Ok, thank you