PLL generates an incorrect 2x clock

[SherwinKim]

Hi!

I'm using 2 PLLs on Arria 10 (10AX027H4F34I3SG) to create  clocks. Both reference clocks are LVDS. The 3 clocks of one PLL are normal. In addition, the 2 clocks of the another PLL output become the set frequency doubling. The worng PLL reference clock is 64 MHz. It sets the output clock to 64MHz and 120MHz, but the actual output frequency is 128MHz and 240MHz. 

Thanks in advance!

[Ash_R_Intel]

Hi,

Is this observation related to simulation or on board measurement?

Regards

[SherwinKim]

Hi,

It has been solved.

The reason is that the pin has external termination and has not been set before.

When the LVDS clock enters the FPGA, the P / N signal will be superimposed occasionally.

[Ash_R_Intel]

Glad to hear that it is resolved.

Regards