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MSP432P401R: How to use differential mode of the ADC embeded in MSP432

user4090349
Intellectual 941 points
Part Number: MSP432P401R
Other Parts Discussed in Thread: ADS8363

MSP432

The ADC in MSP432 has a differential mode. Is it Pseudo-differential or full differential?

I guess the AFE is different for pseudo-differential and full differential.

What kind of AFE is prefer when using differetial mode of MSP432 ADC?

Thanks!

  • 0
    TI__Expert 8510 points

    The MSP432 has full differential inputs for the ADC.  

    In differential mode, the ADC uses the adjacent analog inputs as the positive/negative pairs.  

    For example, if the input channel selected is A0, then Ain+ = A0 and Ain- = A1

    The driverlib code to configure the ADC for differential mode can be found in the  adc14_single_differntial_2s_compliment.c example code in TI Resource Explorer. A code snippet is shown below:

    /* Configuring ADC Memory (ADC_MEM0 A0/A1 Differential) in repeat mode */
    MAP_ADC14_configureSingleSampleMode(ADC_MEM0, true);
    MAP_ADC14_configureConversionMemory(ADC_MEM0, ADC_VREFPOS_AVCC_VREFNEG_VSS,
    ADC_INPUT_A0, true);

    Details of the APIs to configure the ADC can also be found in the Driverlib User's Guide, also available in TI Resource Explorer at dev.ti.com.

    The AFE to use will depend heavily on the sensors you are interfacing to and the environment. If you provide additional information I may be able to direct you better for that question.

  • 0 in reply to Bob Landers
    Intellectual 941 points
    Hello Bob

    Thanks for your feedback.
    If it is full differential ADC, I guess there are two sampling holder capacitor. Could you provide equivalent analog input circuit?

    Could you provide the CMRR of the ADC?

    My sensor is Rogowski Coil. I would like to use it to measure the current. The frequency of the current is less than 42kHz
    And I would like a integral to recover the signal type.

    Thanks!
  • 0 in reply to user4090349
    TI__Expert 8510 points

    The equivalent circuit for the ADC in differential mode is in section 20.2.6.3 of the MSP432 Technical Reference manual.

    The CMRR as shown in the MSP432P401r datasheet Table 5-29 is:

    CMRR_DC = (70,85)  (min, typ)

    CMRR_AC = (55,65)  (min, typ) at 1MHz

    -Bob

  • 0 in reply to Bob Landers
    Intellectual 941 points
    Hello Bob

    Thanks for your feedback. But I think the equivalent circuit in reference manual is for single-end input not for differential input.
    In my consideration, a full differential ADC should have 2 s/h capacitor as ADS8363. Does MSP432 has 2 s/h capacitor.

    Another question is for the CMRR. I guess it only works when in differential mode. Is that correct?

    Thanks!

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