I have been having repeatable issue with the ADF4355-3 where heating up the IC will cause unstable RF output. What I'm seeing is the Lock Detect mux output is toggling between '1' and '0' repeatedly. When I update the registers with a new frequency the output will be stable and no other issue seems to reoccur. I know that the VCO output is dependent on temperature and writing to register 10 will update its temperature. Here's a picture of when the issue occurs https://imgur.com/a/Y9hpF8n. The frequency I was generating is 370MHz.
My question is what's the best way to not have the unstable RF output occur once the IC's registers are set? My application requires the IC to not have any instability due to temperature transitions.
Thank your for your time any advice is greatly appreciated!
Reg10 keeps the temperature related coefficients within the reserved part. You can check figure 36 in datasheet. Reg10=0x00C026BA does not match with the reserved part of Register 10. You need to change…
Can you provide your schematic (at least loop filter and reference input) and register settings?
I won't be able to provide the schematic unfortunately. The differential input comes from the HMC832A and the loop filter is the recommended 35kHz filter from the datasheet.
Note: This is used to generate a 740MHz output, but we have another IC for RF divider by a factor of 2 so it should be 370MHz result.
Reg10 keeps the temperature related coefficients within the reserved part. You can check figure 36 in datasheet. Reg10=0x00C026BA does not match with the reserved part of Register 10. You need to change register 10 as Reg10=0x600026BA.
Figure 36 does not match up with the note. Which states: Bits[DB31:DB14] are reserved. Bits[DB23:DB22] must be set to 11, and all other bits in this range must be set to 0.
Which one is correct?
Figure36 is the correct one.