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ADS8548: Occasional issue in configuring the TI8548

Part Number: ADS8548

Hi,

We are using a ADS8548 in our system, configured via SW mode (SW/HW pins is pulled up), to use internal reference at 2.5V. Configuration register is set to 0x800083FF on system power up.

Most of the time, there is no issue, but at some customers, every once is a while it seems like the device is powered up & configured but for some reason, the reference is 0V instead of 2.5V.

Any issue you are familiar with that may explain this?

Thanks,

Shachar.

  • Hello Shachar,

    We did not see this issue before. Are you using using serial interface? Did you check if the voltage on REFIO pin was 0V or 2.5V when this happened?

    After you programmed CR register, please read back the content of CR to double check by setting bit 30 to 1, then the CR register content will be output on SDO_A with next two accesses(conversions). Please let me know the result after you check, thanks.

    Best regards

    Dale

  • Hi Dale,

    Indeed the REFIO is set to 0.

    We use parallel interface.

    I've checked that CR register and it is not as I'm setting it.

    Any clues why?

    Thanks,

    Shachar.

  • Hi Shachar,

    Can you please let me know what command you sent to ADC and what data you got  when you read back the register contents? Can you please show me the timing plot(/CS,/WR, CONVST, BUSY) when you checked CR register? Also, I suggest to monitor power supply pins and RESET pin to check if the ADC is powered down or there is an interference signal appearing on the RESET pin.

    Thanks&regards

    Dale

  • Hi again Dale,

    W'e're sending the following configuration: "0xC00083ff" and once in a while we get non-sense on the read back.

    We will check on our side if we can see any reason for that.

    Anyway, thanks for your help.

    Shachar.

  • Hi Shachar,

    As you mentioned "I've checked that CR register and it is not as I'm setting it." It looks like your CR register content was changed (the internal reference voltage is still 2.5V after power up).  If you do not plan to change reference voltage, I suggest you to use Hardware mode(HW/SW pin=1) and use internal reference by setting REFEN/WR pin=0 because your programming CR register is doing same thing.

    Also, if you still want to use software mode, I suggest you to try command "0x800083FF" because bit 30 is used to output register contents on SDO_A which is not parallel interface you are using.

    Please notice that "Changes are active with the second WR rising edge in parallel interface mode or with the 32nd SCLK falling edge of the access where the register content is updated in serial mode"

    Thanks&Regards,

    Dale

  • Hi Dale,

    The issue was found to be related to a wrong SOC signal given between the 2 write accesses to the CR register.

    Thanks for you assistance anyway.

    Shachar.