SN65LVPE502B input impedance

Shinichi Inoue

Guru 22311 points

Dear Specialists

My customer has a problem of unconnecting to USB2.0.

He is concerned the spec of input impedance between SN65LVPE502B and EZ-USB FX3(cypress).

He confirmed cypress and got answer.

Could you please see listed below and advise.

Is there any problem in SN65LVPE502B?

--------the answer from cypress--------

This is a compatibility problem between FX3(CYUSB3014) and SN65LVPE502B.

The issue is with the impedance range that the redriver uses when USB 3.0 is disabled.

FX3 will use any impedance value under 150 ohms as a valid super speed impedance, and get into compliance state.

USB spec says impedance under 30 ohms is valid, and USB 2.0 only links should have impedance above 20 K.

There is no description of what should happen between these ranges.

We are using 150 ohms as our threshold.

--------end of answer--------

I appreciate your great help.

Best regards,

Shinichi

over 10 years ago

0 Diego Cortes over 10 years ago

TI__Mastermind 36085 points

Hello,

The Rx impedance when the SS path is disabled (no far- end termination detected in both sides of the re-driver) is the same as the sleep mode Rx termination (ZRX_High_IMP > 50KOhms), this value is out of the valid SS termination, so the cypress chip should take it as SS disconection and try to connect on HS.

Regards,

Diego.

0 Shinichi Inoue over 10 years ago in reply to Diego Cortes

Guru 22311 points

Dear Diego

Thank you for your reply.

I send your answer to the customer.

I think the spec is no problem.

I appreciate your great help.

Best regards,

Shinichi

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SN65LVPE502B input impedance