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MSP430F6725A: Noise Considerations(SD24_B)

DDdoor
Expert 2180 points
Part Number: MSP430F6725A
Other Parts Discussed in Thread: MSP430F6725

Hello,

When measuring with the SD24_B equipped with the MSP430F6725, customers want to eliminate the effects of noise as much as possible.
What should the customer be aware of in addition to the 29.2.11 Grounding and Noise Considerations section of the User Guide (MSP430x5xx and MSP430x6xx Family User's Guide)?

For example, in SD24_B of the code example, after setting the conversion start bit, it moved to LPM0.
Is it effective as a measure against noise?

Is there anything else?

Best regards,
DDdoor

  • 0
    TI__Expert 7015 points

    Hi, DDdoor, 

    There will be expert to answer your questions.

    Thanks, 

    Lixin 

  • 0
    TI__Mastermind 49692 points

    Hello,

    DDdoor said:
    When measuring with the SD24_B equipped with the MSP430F6725, customers want to eliminate the effects of noise as much as possible.
    What should the customer be aware of in addition to the 29.2.11 Grounding and Noise Considerations section of the User Guide (MSP430x5xx and MSP430x6xx Family User's Guide)?

    I would recommend several things.

    • Hardware
      • Follow all external connection (e.g. VDSYS, VASYS) and capacitor (e.g. CVCORE, CVREF) recommendations in the datasheet.
      • Use 0.1 uF decoupling capacitors in parallel with the larger CDVCC and CAVCC capacitors.
      • Use a 0-Ohm placeholder between AVCC and DVCC in case you need to filter digital noise.
      • Use an external reference to achieve greater accuracy if necessary.
      • Use anti-aliasing filters on the ADC inputs to prevent aliasing (noise).
      • Take advantage of the differential inputs to eliminate common-mode noise.
      • Be mindful of the minimum recommended settling time for ADC (affected by external source impedance on ADC pins)
    • Software
      • Make sure the voltage reference has enough time to settle before it's used by the ADC (I'd recommend keeping it on).
      • Use the highest possible oversampling rate (OSR) along with the lowest possible GAIN and take advantage of the entire full-scale range if possible.
      • Use the default 4 sample delay to allow the decimation filter to fill up before reporting a sample.
      • Compensate for the internal offset.

    I may have missed something, but I hope this helps.

    Regards,

    James

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