SBAA535A March   2022  – March 2024 ADC128D818 , ADS1000 , ADS1000-Q1 , ADS1013 , ADS1013-Q1 , ADS1014 , ADS1014-Q1 , ADS1015 , ADS1015-Q1 , ADS1018 , ADS1018-Q1 , ADS1100 , ADS1110 , ADS1112 , ADS1113 , ADS1113-Q1 , ADS1114 , ADS1114-Q1 , ADS1115 , ADS1115-Q1 , ADS1118 , ADS1118-Q1 , ADS1119 , ADS1120 , ADS1120-Q1 , ADS112C04 , ADS112U04 , ADS1130 , ADS1131 , ADS1146 , ADS1147 , ADS1148 , ADS1148-Q1 , ADS114S06 , ADS114S06B , ADS114S08 , ADS114S08B , ADS1158 , ADS1216 , ADS1217 , ADS1218 , ADS1219 , ADS1220 , ADS122C04 , ADS122U04 , ADS1230 , ADS1231 , ADS1232 , ADS1234 , ADS1235 , ADS1235-Q1 , ADS1243-HT , ADS1246 , ADS1247 , ADS1248 , ADS124S06 , ADS124S08 , ADS1250 , ADS1251 , ADS1252 , ADS1253 , ADS1254 , ADS1255 , ADS1256 , ADS1257 , ADS1258 , ADS1258-EP , ADS1259 , ADS1259-Q1 , ADS125H01 , ADS125H02 , ADS1260 , ADS1260-Q1 , ADS1261 , ADS1261-Q1 , ADS1262 , ADS1263 , ADS127L01 , ADS1281 , ADS1282 , ADS1282-SP , ADS1283 , ADS1284 , ADS1287 , ADS1291 , LMP90080-Q1 , LMP90100 , TLA2021 , TLA2022 , TLA2024

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Data Sheet Timing and Nomenclature
  6. 3 What Causes Conversion Latency in a Delta-Sigma ADC?
  7. 4 Digital Filter Operation and Behavior
    1.     8
    2.     9
    3. 4.1 Unsettled Data Due to an ADC Operation
  8. 5 ADC Features and Modes that Affect Conversion Latency
    1. 5.1 First Conversion Versus Second and Subsequent Conversion Latency
    2. 5.2 Conversion Mode
    3. 5.3 Programmable Delay
    4. 5.4 ADC Overhead Time
    5. 5.5 Clock Frequency
    6. 5.6 Chopping
  9. 6 Analog Settling
  10. 7 Important Takeaways
  11. 8 Cycle Time Calculation Examples
    1. 8.1 Example #1: Using the ADS124S08
    2. 8.2 Example #2: Changing the Conversion Mode
    3. 8.3 Example #3: Changing the Filter Type
    4. 8.4 Example #4: Changing the Clock Frequency
    5. 8.5 Example #5: Enabling Chop and Reducing the Number of Conversions per Channel
    6. 8.6 Example #6: Scanning Two Channels With Different System Parameters
    7. 8.7 Example #7: Using the ADS1261
    8. 8.8 Example #8: Changing Multiple Parameters Using the ADS1261
  12. 9 Summary
  13. 10Revision History

Abstract

Many precision data acquisition applications are constrained by a system cycle time, or the total time required to perform one complete loop through all measurement channels. However, it is not always clear how this metric correlates to the information provided in a delta-sigma analog-to-digital converter (ADC) data sheet, which may include multiple features and modes that affect the rate at which the device outputs data. To provide a deeper understanding of how to calculate the system cycle time using the ADC data sheet information, this application note offers a detailed discussion of the most important factors that affect ADC conversion latency. Additionally, key takeaways are summarized and several examples using actual ADCs are provided.