TUSB1044: TUSB1044 LFPS Equalization

Kazuki Kuramochi

Part Number: TUSB1044

Hello professional,

My customer has question for TUSB1044's LFPS Equalization.

As datasheet ｐ43 mentioned, LFPS signal is applied EQ setting when We whet LFPS_EQ set "1". Could you show how large is the equalization of LFPS signal?

Best regards,

Kazuki Kuramochi

over 6 years ago

0 David (ASIC) Liu over 6 years ago

TI__Guru**** 177856 points

Kazuki-san

The equalization level would depend on the setting of URX[2:1]EQ_SEL, UTX[2:1]EQ_SEL, DRX[2:1]EQ_SEL, and DTX[2:1]EQ_SEL.

With LFPS being a low-speed signal, you generally don't need to set equalization for LFPS.

Thanks
David

0 Kazuki Kuramochi over 6 years ago in reply to David (ASIC) Liu

TI__Genius 10565 points

David-san,

Thank you for your prompt reply.

I know LFPS equalization dependent on the other EQ setting. The datasheet has Equalization performance, the graph of Equalization Linear performance and EQ setting curve for high speed signal line. However the datasheet don't has similar data and graph for equalization performance for LFPS. It is just mentioned LFPS will equalize and not indicate any data.
Could you provide the specification performance of LFPS equalizer?

Best regards,
Kazuki Kuramochi

0 David (ASIC) Liu over 6 years ago in reply to Kazuki Kuramochi

TI__Guru**** 177856 points

Kazuki-san

Unfortunately, we do not have the characterization data for LFPS as we typically don't apply equalization to a 20MHz clock waveform. In fact, applying equalization could actually cause LFPS to fail certain USB compliance tests.

Thanks
David

0 Kazuki Kuramochi over 6 years ago in reply to David (ASIC) Liu

TI__Genius 10565 points

David-san,

Would you provide the reason why don't you have the characterization data for LFPS and why does it has concern for causing LFPS to fail usb compliance tests?

I think LFPS signal data rate is in the red square at at the below graph of EQ setting and EQ gain is following this characteristics. So I guess that you mentioned you didn't has the characterization data. Is this guess correct?

Best Regards,

Kazuki Kuramochi

0 David (ASIC) Liu over 6 years ago in reply to Kazuki Kuramochi

TI__Guru**** 177856 points

Kazuki-san

Applying equalization to LFPS could cause LFPS signal amplitude to exceed the peak to peak voltage (min 800mV and max 1200mV) as part of the USB compliance test.

The EQ gain characterization curve uses a different frequency pattern than the LFPS pattern, the gain response would be different.

The LFPS is a 10-50MHz clock signal, the attenuation to the LFPS due to PCB insertion loss would be minimal, why would you want to apply equalization to LFPS?

Thanks
David

0 Kazuki Kuramochi over 6 years ago in reply to David (ASIC) Liu

TI__Genius 10565 points

David-san,

Would you discuss about this topic by mail?
I will send you mail. Please find it.

Thank you,
Kazuki Kuramochi

0 David (ASIC) Liu over 6 years ago in reply to Kazuki Kuramochi

TI__Guru**** 177856 points

Direct support through email, close the thread.

Thanks
David

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TUSB1044: TUSB1044 LFPS Equalization