During testing these past couple of months we've noticed some 'pll wobbles' affecting HD VGA screens. The wobbles can be brought on by excessive PLL divisors and/or elevated temperature (approx low to mid 50 C's surface temperature, higher than P2-Eval board can naturally get to with its own self heating).
In this thread we'll try and get some numbers together. Also if anyone has ideas for some kind of automated detection when the wobbles occur, that would help. I can't spot it on the PLL current drawn through V2831 unfortunately, and only just on the DMM in frequency mode, and then only visually
The photo below has a shutter time around 1/30 sec which probably means it has two stacked frames. I'll try and get a shot with 1/60 sec to match the vertical refresh. The test pattern is a black and white grid, single white lines are 32 pixels apart in X direction and 20 pixels apart in Y direction.
If a pixel deviates + / - 7 pixels in the X direction, I believe that translates to + / - 50 nsec
We're also using a PLL divisor of 14 to hit 138.57 MHz (1920x1080 60fps with reduced blanking 1), things are generally better and divisors of 2 or 3
I need to do some more work on hsync to make sure there's not something else going on, however we have done testing with a pin exporting clock_freq/1000 and it does show the wobble simultaneously with the video wobble.
Pnut_v32i test code also attached