• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 79 subscribers
  • Views 816 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.

MSP430F47177: How do I calculate the conversion time required for sigma delta ADC.

Preeti Bhosale
Prodigy 60 points
Part Number: MSP430F47177

Hey, I am considering to use the MSP430F47177 in one of my applications however I wanted some clarification on how i can could calculate the time required for the conversion of the input signal by the sigma delta adc.

i read the user guide supplied by TI for "MSP430x4xx Family" under chapter 29 in the SD 16 operation it is stated that the SD16 module has an input modulator frequency of up to 1 Mhz does this mean that the amount of time require to convert the input waveform into its equivalent digital output is equivalent to 1/1Mhz or 1us. Basically how long does it take for the adc to begin taking a new reading?

I want to use an external multiplexer with the already provided adc, I need to find out what is the maximum number of input signals I can provide ensuring a good sampling rate on the input signal even with the external multiplexer?

  • 0
    TI__Genius 13740 points

    Hello,

    The conversion time (sampling period) for the SD ADC is based on the modulation frequency and the over-sampling rate (OSR). The sampling frequency is equal to the modulation frequency divided by the OSR, thus the sampling period would be the reciprocal of that. You can read through the SD16_A chapter of the device family user's guide for more information on this.

    Best regards,

    Matt

  • 0 in reply to Matt Calvo
    Prodigy 60 points

    Hey Matt, 

    Are there any parameters for the selection of OSR  or can we keep 1 to have a faster sampling rate along with a modulator frequency of 1.Mhz ?

    Thanks.

  • 0 in reply to Preeti Bhosale
    TI__Genius 13740 points

    Preeti,

    As explained in the user's guide, the OSR can be configured using the SD16OSRx bits in the SD16CCTLx register ( Chapter 30 Page 24 ):

    Best regards,

    Matt

  • 0
    Guru 88880 points

    You should be careful about using an external multiplexer. A sigma-delta ADC works best when it's always connected. (That's why there are 7 ADCs.)

    Each time you switch channels on your external multiplexer, you should plan to throw out the next 3 readings. SD16INTDLY won't be effective since the ADC won't know, [Ref User Guide (SLAU056L) Sec 30.2.12]

**Attention** This is a public forum