AD5293 value always 2/3 steps lower

Greetings,

  I have been trying to use some AD5293 digpots to get the complete range of some ADC equipment. It works mostly fine, but for some reason, there seems to be a small error, that is, if I set the digpot to 100, most of the time when I read back it says the value is 98. but then, sometimes, it will get the correct value (But this happens rarely), but when we get this small offset, it does not increase with higher values, if I set it to 900, then I may get 897.

 Does this happen to everyone? Is there any workaround? For larger values is not that big of an issue, but for smaller ones, it is... specially because we use 10 digpots in series, so error does accumulate.

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  • Yes, I mean the value for the reading command after setting the digpot up.

    The proccess is:

     1) write enable (No problem, wiper does not move if this is not sent) [Command 4, set RDAC register write protect to 1]

     2) write value (Everything seems to be ok, let's say I wrote "50") [Command 1]

    small wait (0.5 seconds, just in case)

     3) Read value (I read "48") [Command 2]

    For this test, I have not daisy chained them, every digpot is alone with it's chip select

    For the config, I just left it as it is ( Calibration enable = 0). Everything is done as shown in page 19 of the datasheet.

  • 0
    •  Analog Employees 
    on Mar 3, 2021 5:01 AM in reply to Jetomad

    Please provide the SDI and SDO data for the entire command step sequence and the schematic.

    Also, please provide a scope shot of the write and read frames. 

    It is certainly not possible for the register readback to be different from what you have written through SDI..