A problem about AD7324

Hi everyone,

   I met a quite curious problem recently. I used AD7324 on my board to sample anolog signals, and the power supply are +-15V, +5V and 3.3V. I am seeing the ADC could be locked up sometimes. Everytime the promblem present, the 4 channels of AD7324 output data 0x8 although the channel number changes nomally.This output data would not recover to normal until power down and up again, even i config the command register to work in normal operation every 500us via SPI. I don't know how does this happen, and by the way, the problem would be occur from power up every time.

  Anyone can tell me why? Thanks a lot!

  • 0
    •  Analog Employees 
    on Aug 11, 2015 6:41 PM

    Hi,

    Stuck codes would usually mean an issue with the reference circuit. This article here might help you. I could also have a look at your schematics if you attach a copy here.

     

    Regards,

    Karen

  • Hi KarenNE,

      Thanks for your reply. I checked the PDF and found the wave form on figure 9 is quite similar with my trouble, i would check my board at the reference. The schematics is not in my computer now, maybe i'would attach it tommorrow if i couldn't fix it tonight. Thanks a lot!

  • Hi KarenNE,

       I havn't fix my problem yet, and i attached my schematic below. I used one ADR443 to generate refference VREF for 3 AD7324. As to the PDF file, ceramic capacitors may be the first factor to "stuck" code, but i put 3 capacitors at the output pin of ADR443, and 2 capacitors at the VREF pin of each AD7324, i think the persability of capacitor could be emililated.The second, the PCB has 6 layers, with 2 whole ground, signals have been burid between the 2 ground layers; The third, ADR443 can output 10mA current max, and the static current of AD7324 is only 1uA, so i think supply currrent of VREF should be enough. Could you help me to check the problem again?

    Regards,

    Huang.@

    @

  • 0
    •  Analog Employees 
    on Aug 18, 2015 9:57 PM

    Hi,

    Have you monitored your reference during operation? How are the capacitors placed with respect to the AD7324 REFIN pin?

    Regards,

    Karen

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:09 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin