ADAU1446 CLKOUT modulating

Hi. I've built a prototype using the ADAU1446 using the CLKOUT as fs*256 to clock a CODEC. It's working and I'm not conscious of any problems with the output signals that might be caused by the master clock. However, CLKOUT appears to be frequency modulating at about 24kHz (fs=48kHz), the oscillator itself is stable. As best as I can tell fs is also stable. Any ideas? Is this something I'm likely to see using the fs*256 option? Would I be better using the buffered oscillator? tia Gordon

Parents
  • Hi Brett. Thanks for the response. You've given me some pointers so I'll cut a few tracks and pull a few R's before troubling you further. I'll post back if I can narrow the problem down a bit.

    I'll try and get some scope shots anyway but it might not be very informative. I check it by setting the A time base to 0.5us then increasing the delay on the delayed trace set at 0.05us. As you increase the delay you see what looks like jitter but as it approaches ~4.2 the 'jitter' disappears. Increase the delay further and the 'jitter' comes back to disappear again at ~8.4. So what you see depends on the delay position.

    Doesn't do it until it's been compiled if it helps. I've had the circuit right down to a minimal setup so don't /think/  it's down to the circuit itself. I'll have another basic circuit test tomorrow.

    Cheers

    Gordon

Reply
  • Hi Brett. Thanks for the response. You've given me some pointers so I'll cut a few tracks and pull a few R's before troubling you further. I'll post back if I can narrow the problem down a bit.

    I'll try and get some scope shots anyway but it might not be very informative. I check it by setting the A time base to 0.5us then increasing the delay on the delayed trace set at 0.05us. As you increase the delay you see what looks like jitter but as it approaches ~4.2 the 'jitter' disappears. Increase the delay further and the 'jitter' comes back to disappear again at ~8.4. So what you see depends on the delay position.

    Doesn't do it until it's been compiled if it helps. I've had the circuit right down to a minimal setup so don't /think/  it's down to the circuit itself. I'll have another basic circuit test tomorrow.

    Cheers

    Gordon

Children
No Data