SLAA957 September   2020 MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253 , MSP430F2003 , MSP430F2013 , MSP430F2013-EP , MSP430F423A , MSP430F4250 , MSP430F425A , MSP430F4260 , MSP430F4270 , MSP430F427A , MSP430F47126 , MSP430F47127 , MSP430F47163 , MSP430F47166 , MSP430F47167 , MSP430F47173 , MSP430F47176 , MSP430F47177 , MSP430F47183 , MSP430F47186 , MSP430F47187 , MSP430F47193 , MSP430F47196 , MSP430F47197 , MSP430F477 , MSP430F478 , MSP430F4783 , MSP430F4784 , MSP430F479 , MSP430F4793 , MSP430F4794 , MSP430F6720 , MSP430F6720A , MSP430F6721 , MSP430F6721A , MSP430F6723 , MSP430F6723A , MSP430F6724 , MSP430F6724A , MSP430F6725 , MSP430F6725A , MSP430F6726 , MSP430F6726A , MSP430F6730 , MSP430F6730A , MSP430F6731 , MSP430F6731A , MSP430F6733 , MSP430F6733A , MSP430F6734 , MSP430F6734A , MSP430F6735 , MSP430F6735A , MSP430F6736 , MSP430F6736A , MSP430F6745 , MSP430F67451 , MSP430F67451A , MSP430F6745A , MSP430F6746 , MSP430F67461 , MSP430F67461A , MSP430F6746A , MSP430F6747 , MSP430F67471 , MSP430F67471A , MSP430F6747A , MSP430F6748 , MSP430F67481 , MSP430F67481A , MSP430F6748A , MSP430F6749 , MSP430F67491 , MSP430F67491A , MSP430F6749A , MSP430F67621 , MSP430F67621A , MSP430F67641 , MSP430F67641A , MSP430F6765 , MSP430F67651 , MSP430F67651A , MSP430F6765A , MSP430F6766 , MSP430F67661 , MSP430F67661A , MSP430F6766A , MSP430F6767 , MSP430F67671 , MSP430F67671A , MSP430F6767A , MSP430F6768 , MSP430F67681 , MSP430F67681A , MSP430F6768A , MSP430F6769 , MSP430F67691 , MSP430F67691A , MSP430F6769A , MSP430F6775 , MSP430F67751 , MSP430F67751A , MSP430F6775A , MSP430F6776 , MSP430F67761 , MSP430F67761A , MSP430F6776A , MSP430F6777 , MSP430F67771 , MSP430F67771A , MSP430F6777A , MSP430F6778 , MSP430F67781 , MSP430F67781A , MSP430F6778A , MSP430F6779 , MSP430F67791 , MSP430F67791A , MSP430F6779A , MSP430FE423 , MSP430FE4232 , MSP430FE423A , MSP430FE4242 , MSP430FE425 , MSP430FE4252 , MSP430FE425A , MSP430FE427 , MSP430FE4272 , MSP430FE427A , MSP430FG4250 , MSP430FG4260 , MSP430FG4270 , MSP430FG477 , MSP430FG478 , MSP430FG479 , MSP430FG6425 , MSP430FG6426 , MSP430FG6625 , MSP430FG6626 , MSP430FR5041 , MSP430FR5043 , MSP430FR50431 , MSP430FR6005 , MSP430FR6007 , MSP430FR6041 , MSP430FR6043 , MSP430FR60431 , MSP430FR6045 , MSP430FR6047 , MSP430FR60471 , MSP430I2020 , MSP430I2021 , MSP430I2030 , MSP430I2031 , MSP430I2040 , MSP430I2041

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction: MSP Sigma-Delta ADCs and Common Applications
  4. 2MSP Sigma-Delta ADC Portfolio
  5. 3Sigma-Delta ADC Overview
  6. 4MSP Sigma-Delta ADC Features
    1. 4.1  ADC Inputs: Differential or Single-Ended
    2. 4.2  Input Channels: Independent or Multiplexed
    3. 4.3  Integrated Buffers
    4. 4.4  Integrated PGAs
    5. 4.5  Offset Calibration: Internal or External
    6. 4.6  Voltage Reference: Internal or External
    7. 4.7  ADC Modulator Clock Frequency: Fixed or Adjustable
    8. 4.8  Sampling Rate versus Data Rate
    9. 4.9  Conversion Mode: Single or Continuous
    10. 4.10 Groups of ADC Channels
    11. 4.11 Preload
    12. 4.12 Output Format: Unipolar or Bipolar Data
    13. 4.13 Module Synchronization
    14. 4.14 Architecture: Discrete-Time versus Continuous-Time
  7. 5Solutions to Common MSP Sigma-Delta ADC Configuration Issues
    1. 5.1 ADC Input Configuration
      1. 5.1.1 Settling Time Exceeds Recommended Minimum
      2. 5.1.2 Amplitude of the Input Signal Exceeds FSR
      3. 5.1.3 Missing Anti-Aliasing Filters
    2. 5.2 ADC Clocking Configuration
      1. 5.2.1 Incorrect Sampling Frequency
    3. 5.3 ADC Results
      1. 5.3.1 Unexpected Output Data Format
      2. 5.3.2 Low Resolution
      3. 5.3.3 Data Interpretation
    4. 5.4 Reference Module (REF) Configuration
      1. 5.4.1 Choosing Between an Internal or External Reference
      2. 5.4.2 Connecting the Recommended Capacitors
      3. 5.4.3 Delaying Conversions Until the Reference Settles
    5. 5.5 Hardware Recommendations
  8. 6Frequently Asked Questions
  9. 7References

5.4.3 Delaying Conversions Until the Reference Settles

After turning on the internal or external reference, make sure to start the conversions after the reference has settled completely. Otherwise, the reference may not stabilize which could introduce noise in the digital output. The reference can be left on continuously or manually toggled off and on between conversions to save power. Some modules such as the SD24_B automatically power down the internal reference between conversions. The device-specific data sheet should specify the reference turn-on or settling time. The reference voltage can be measured externally using an oscilloscope during start up or during conversions to detect instability. Note that the oscilloscope probe may impact the capacitance observed on the reference pin and affect the conversions.