We are seeing issues when using a 10MHz external reference for the AD9361, ... when using this reference frequency the BB PLL calibration times-out resulting in a fail. We have checked the reference clock waveform into the chip and it is a 'Square' wave with a peak amplitude of ~1.1Vpp.
Previously we have used a 40MHz external reference with a similar waveform shape and amplitude and had no issues with calibration or operation.
As further investigation we checked a variety of Reference clock frequencies and found that we could pass the BB PLL calibration only if the reference input frequency was greater than ~13MHz.
We noticed that there was a post on this forum from April 22, 2015, reporting similar issues, although there was no real resolution to the question posted at that time. However, that poster made mention that he had better success if the 10MHz waveform was a sine wave, ... We also tried this option and also found that the BB PLL calibration passed if the 10MHz was a sine wave instead of a square wave.
Can you please provide some guidance? Are there any special Clock or PLL settings that are required for a 10MHz reference signal? Is there some limit to the harmonic content that must be observed for lower reference frequencies?
Are you doing everything shown in post 21 of https://ez.analog.com/message/202363#202363 ?
Yes we have pulled in the latest updates and applied the recommended settings that are referenced in that post, but are still unable to lock with an external 10MHz reference. Actually from the series of exchanges in that post, it is not clear that the original poster's problem was ever resolved as the responses from user 'test1' indicate that they were still having issues as of early June.
I have seen mention of this issue frequently enough in this forum to surmise that this is a general issue either with the chip, the firmware or both.
We are looking for a clear explanation of what the fundamental issue is and how to make the system work with an external 10MHz reference.
Request being handled via direct field support.
CMC-B if your field support was successful would you mind sharing any outcomes here?
There is no resolution yet for 10MHz square wave reference clock. You can use 10MHz sine wave reference clock which works fine. I don't know if that can be supported in your system.