AD5932 Frequency ramp is sometimes not started

I have successfully configured the AD5932 in automatic frequency ramp mode. The ramp is started periodically by a single pulse at the CTRL pin and this works in most cases (99% of times).

But sometimes (1% of times) the ramp is not started correctly! It seems like the AD5932 recognizes the CTRL pin  because the start frequency is loaded correctly but the ramp is not started afterwards!

I do not reconfigure something over SPI during run-time (FSYNC is kept high). The Interrupt and Standby pin are not used (kept low) during run-time.

Are there any known issues with the AD5932 device or do you have any advises? Thanks!

  • 0
    •  Analog Employees 
    on Apr 13, 2018 7:51 AM

    Hi,

    As far as I knwo there is not any problem with this devices.. and it is many years in the market.

    Looks like your problem is related to the digital state machine... and this is a little bit strange as it is a digital machine...

    Could you send a plot showing when the device fail, including Vout, Mclk, CTRL, and FSYNC pins, please?

    Regards,

    Miguel

  • 0
    •  Analog Employees 
    on Apr 13, 2018 9:25 AM

    Hi,

    As not sure from were it comes the blue channel... could you trigger the scope with CTRL signal?

    BTW... How is configured the device increments?

    Regards,

    Miguel

  • Hi, thank you for your response.

    I have attached the requested plots. I couldn't include the FSYNC signal because I used another signal for triggering and I have only 4 channels. But the FSYNC is kept high during run-time (this was verified with an other measurement).

    CH1 (yellow): CTRL

    CH2 (blue): Helping signal for triggering

    CH3 (red): VOUT

    CH4 (green): MCLK

    Zoomed:

    Regards

  • Hi,

    No I can't, because the CTRL line is the same for every cycle, so I cannot trigger a "bad" cycle. Nonetheless the FSYNC signal is High all the time, you wouldn't get any new information.

    Frequency increment: 360 ns -> TInt = 18, TimeBaseMultiplier: 1

    Number of increments: 4095

    My feeling is that the device is correctly configured because it works in most cases...

    Regards,

  • 0
    •  Analog Employees 
    on Apr 13, 2018 2:57 PM

    then.. from where comes the blue line?