AFE7950: Driving REFCLK pins with a differential source

Evgeniy Fedosov

Part Number: AFE7950
Other Parts Discussed in Thread: LMK04828

Hi everybody!

I got the question about reference clock input REFCLK. There is no suitable information about circuits and connecting, like for example LMK04828 datasheet section: "Driving CLKin and OSCin Pins With a Differential Source".
Where I can find this information?

over 3 years ago

0 Vijayendra Varma Siddamsetty over 3 years ago

TI__Genius 10865 points

Hi Evgeniy,

Ref clock input electrical characteristics are given in section 7.7 of Datasheet. It's in page 24 and 25.

It can be driven as shown in the EVM, from LMK04828 output with AC coupling and LMK output mode set to LVDS.

Also note that as the full datasheet is not public, questions related to full DS can be sent to the email ID mentioned at the end in secure folder web page (www.ti.com/mysecuresoftware).

Regards,

Vijay

0 Evgeniy Fedosov over 3 years ago in reply to Vijayendra Varma Siddamsetty

Intellectual 510 points

Hi Vijay!

Thanks, I saw datasheet and EVM. But I can't find information about internal circuits - is there internal pull-up or/and pull-down resistors to provide required Vdiff and Vcom?

+1 Vijayendra Varma Siddamsetty over 3 years ago in reply to Evgeniy Fedosov

TI__Genius 10865 points

Hi Evgeniy,

Ref clock input has to be AC coupled. Vcom is set by the AFE. Differential impedance is 100 ohm.

Regards,

Vijay

0 Evgeniy Fedosov over 3 years ago in reply to Vijayendra Varma Siddamsetty

Intellectual 510 points

Vijayendra Varma Siddamsetty said:
Vcom is set by the AFE.

Hi Vijay!

This is what I needed to know. Thank you!

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AFE7950: Driving REFCLK pins with a differential source