LMK01010: How to use LVDS to drive LMK01010 input. LMK61E2 as ClokIn LVDS

Sergio Pavesi

Part Number: LMK01010
Other Parts Discussed in Thread: LMK61E2, LMK01000, LMK02000

Good Morning / Afternoon,

thanks for your time and support until now.

I have some problem with the datasheet of LMK01010.

From the datasheet is difficult to clearly understand if LMK01010 has already an internal bias or not. From the general presentation at page 20 of https://www.ti.com/lit/ds/symlink/lmk01010.pdf it appears so but the termination is placed "incorrectly", at least according figure 6 of https://www.ti.com/lit/an/slaa840/slaa840.pdf (even assuming internal bias).

Incorrect for LVDS, Fig 13

Correct for LVDS, FIG 6

Which one of the figures is correct for LVDS Input of LMK01010?

If the bias is not internally given by LMK01010, could I use Figures 4 or 5 of https://www.ti.com/lit/an/slaa840/slaa840.pdf

Please not that

https://e2e.ti.com/support/clock-timing-group/clock-and-timing/f/clock-timing-forum/828235/lmk01010-can-i-use-lvds-to-drive-lmk01010

do not answer to my question.

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Could I use LMK61E2 as input clock?

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Thanks for your time

over 2 years ago

+1 Ajeet Pal over 2 years ago

TI__Genius 12550 points

Hi Sergio,

Termination will be determine based on receiver datasheet. As the LMK01010 datasheet mentioned, LMK01000 family devices required OSCin inputs (CLKin) AC coupled and it internal biases the signal to the proper DC level.

In that case, the datasheet provided termination should work and you can use LMK61E2 LVDS output to this device.

Regards,

Ajeet Pal

0 Sergio Pavesi over 2 years ago in reply to Ajeet Pal

Prodigy 60 points

Hi Ajeet,

thanks for your time.

sorry but the datasheet is not clear for the reason also reported by

https://e2e.ti.com/support/clock-timing-group/clock-and-timing/f/clock-timing-forum/219116/lmk01000-terminations (if I have found this answer berore I will not have posted my question about the 100 Ohm before or after the capacitor). I am always wary that some chip could decide to not completely follow standard if not specified otherwise.

Timothy T "Yes. Earlier in the datasheet at the pin descriptions a comment is made about the pin compatible nature of the LMK010x0 with the LMK02000 and LMK030xx families. This is were the copy-paste comes from. I think you're right it would be more clear in the latter part of the datasheet if we used the actual pin names for this specific device vs. the pin compatible names of the other devices."

Timoty will basically advise to use case B aka LVPECL equivalent of LVDS Fig 6 of https://www.ti.com/lit/an/slaa840/slaa840.pdf that is not the fig 13 of https://www.ti.com/lit/ds/symlink/lmk01010.pdf

Thanks for your time.

Best Regards

0 Ajeet Pal over 2 years ago in reply to Sergio Pavesi

TI__Genius 12550 points

Hi Sergio,

Yes, I agree the datasheet should be specified with the correct pin names.

So for now, I think you got termination recommendation for LVDS input.

Regards,

Ajeet Pal

0 Sergio Pavesi over 2 years ago in reply to Ajeet Pal

Prodigy 60 points

Hi Ajeet,

thanks for your time.

Yes, I consider this issue resolved. I have already voted as "This resolved my issue"

Best Regards,

Sergio

Clock & timing

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LMK01010: How to use LVDS to drive LMK01010 input. LMK61E2 as ClokIn LVDS