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ADS1248: ADC Sampling Configuration

Part Number: ADS1248
Other Parts Discussed in Thread: ADS1148

Hello E2E Experts.

Good day.

I am using the ADS1248 chip recently. There are some problems with the ADC sampling configuration, I use an internal reference voltage of 2.048v, then the positive channel is 0, the negative channel is 1, the gain is PGA1, and the FSC is not set. When the voltage I sample is 2.048v, the ad sampling value is not 8388607, Do you need to see my initialization and sampling configuration?

Thank you in advance.

Regards,

CSC

  • Hi CSC,

    What code value do you receive under these circumstances, if it is not full scale (8388607)? Is it close? Is it way off?

    How is the voltage being set? In other words, what is the absolute voltage on AIN0 (relative to ground) and what is the absolute voltage on AIN1 (relative to ground)?

    Are you using a unipolar or bipolar power supply?

    -Bryan

  • Hello Bryan,

    Good day.

    I use a unipolar power supply. The AIN0 to the ground is 1.528v, and the AIN1 to the ground is -0.504v. At full scale, the value read is as shown in the picture:

    Regards,

    CSC

  • Hi CSC,

    If you are using a unipolar supply, then none of the applied input signals can be less than ground. Therefore, AIN1 cannot be at -0.5V, it must be >0V. See Section 9.3.2.1 in the ADS1148 datasheet

    Please also see Table 7.1 Absolute Maximum Ratings. You are violating these ratings because the maximum absolute input voltage should be no less than AVSS-0.3V.

    -Bryan