Regarding drive strength

[surendrajadhav]

Hi,

We are working on ENET2 interface of i.MX6UL. We have observed one thing that when we keep drive strength enable value for ethetnet signals (except clock) to 240 ohm, ethernet communication work.

However if we make drive strength enable to 40 ohm, ethernet communication does not work.

Can you clarify that reducing drive strength enable value reduces drive strength of the pin and increasing drive strength enable value increases drive strength of the pin?

We thought that when we increasing value for 240 ohm, it reduces current as per ohms law and 40 ohm increase current value and thereby drive strength.

Please confirm.

Regards,

Surendra

[Yuri]

Hello,

  Board's signals trace impedance should match outputs and inputs impedance.

Please look at section 3 (i.MX 6UltraLite layout recommendations) of the

Hardware Development Guide.

https://www.nxp.com/docs/en/user-guide/IMX6ULHDG.pdf 

Have a great day,
Yuri

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[surendrajadhav]

Hi Yuri,

Thanks a lot for your reply.

However our concern is with drive strength and not with ODT(On Die Termination).

We are confused about drive strength that increasing resistor value (on chip strength resistance value between 34 ohm to 240 ohm) increases drive strength and reducing value reduces drive strength.

Regards,

Surendra

[Yuri]

Hello,

  the drive strength is equivalent of output impedance.

Regards,

Yuri.