• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 78 subscribers
  • Views 1028 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SD24_B MSP430F67791 - What is the Effective Number of Bits and how to measure the Offset

Pedro Medeiros
Prodigy 20 points
Other Parts Discussed in Thread: MSP430F67791

Hi,

I am working with the MSP430F67791 and could not find in the datasheet or in the Family User's Guide the Effective Number of Bits (ENOB) for a certain oversampling ration. Is there any formula about that?

Another doubt is about how to measure the offset of the PDA and the modulator.

Thanks, 

  • 0
    TI__Guru**** 202096 points
    Hi Pedro,

    ENOB = (SINAD-1.76)/6.02, where various SINAD values are provided in the MSP430F67791 datasheet based off of the SD24GAIN selected.

    With SD24CAL = 1, the offset of the modulator and PGA can be measured in a single conversion and calibrated in software afterwards. Setting SD24CAL shorts the inputs so the value measured can be used as an offset error for the actual measured signals.

    Regards,
    Ryan
  • 0 in reply to Ryan Brown1
    Prodigy 20 points
    Hi Ryan.
    Thank you for the fast response.
    I had already calculated the effective number of bits as you described, but didn't quite believe the result I got. Wouldn't that make the cap (OSR =1024 and PDA gain = 1) to be approximately 16 bits (SINAD = ~99dB)? So not even in the best case scenario am I able to get a result close to 24 bits?
  • 0 in reply to Pedro Medeiros
    TI__Guru**** 202096 points
    Hello Pedro,

    You are correct, the ENOB of the MSP430F67791 is between 9.84 and 15.49 bits.

    Regards,
    Ryan

**Attention** This is a public forum