my AD9958s work well in room temperature condition. But when they are heated up to 60 degree celsius for some hours, there usually happen problems such as the system frequency/4 at the pin 54 (Sync Clk) varies (PLL unlocked) and sometimes the output frequency is shifted some 100Hz.
The problem is common for almost all my 50 AD9958s.
In my design, the reference frequency is around 25MHz, and the multiplier inside is set up to 20 (it is the maximum value). Only channel 0 is turned on. And other configuration is the same to the EVKIT and is proven to work well in normal conditions.
I still do not know why the AD9958 work so bad in high temperature ranges while the operation temperature is described as -40~85 degree celsius in datasheet.
Could you please diagnose the symptoms for me? By the way, do you support industrial grade AD9958s?
Thank you very much indeed!