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ADS1158: ADS1158 data readout problem (output scaling)

DavidS
Prodigy 10 points

Part Number: ADS1158

Hello,

I'm using an ADS1158 ADC to readout 16 channels of 0-5V inputs, Vref is 5V, supplied by an REF5050 Source.

I'm not using an analog buffer between the internal MUX and the ADC.

My problem is the following:
If I set VREF at an AIN-Pin, an read out the data, I get 32767 (0x7FFF) counts at this channel, which means if I can beliebe the datasheet, that the voltage would be 1.06*VREF, which is in fact definitely not correct.
Corresponding to the datasheet the readout of the channel should be 0x7800.

VREF is really 5V, I checked this several times, with different Multimeters (for exmample an HP 34401A).

Have you any ideas why this discrepancy (0x7FFF vs. 0x7800) occurs?

Best regards

  • 0
    TI__Guru** 113765 points
    Hi David,

    Welcome to the E2E forum! Did you check your analog supply voltage? AVDD must be within 100mV of the REF5050. Have you tried looking at the reference monitor?

    Also, have you tried another voltage other than the reference as a sanity check? Can you send me your schematic and register configuration?

    You might want to check your solder connections. Sometimes these QFNs are difficult to get good solder connections if you have hand soldered the device.

    Thanks,
    Bob B