ppm offset on clock data recovery

[jugemu1234]

Hi

Pls give me some help to solve my confusion.

In case a CDR has +/-2000ppm offset tracking ability, is this 2000ppm only on data or only on reference clock?

I think certain ppm from one data rate is much smaller than same ppm from reference clock, assuming some multiplication in Rx PLL.
For example, data is 10Gbps and ref clk is 100MHz.
+2000ppm(0.2%) of 10Gbps(1UI=100ps) is just 0.2ps but +2000ppm on 100MHz(1period=10ns) is as much as 20ps.

Thanks,

 

[leo_o2]

It means tracking to reference clock.