SDAA451 July   2026 ADS131M08

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2What is phase shift and phase error?
  6. 3How to calibrate out phase error with the ADS131M08
    1. 3.1 Determining the phase error
    2. 3.2 Converting to the time domain
    3. 3.3 Converting to modulator clock cycles
    4. 3.4 Converting to binary and writing to the PHASEn[9:0] bits
    5. 3.5 Phase calibration considerations
    6. 3.6 Summarizing the phase calibration process
    7. 3.7 Using the Phase Calibration Feature
      1. 3.7.1 Phase calibration considerations examples
  7. 4Synchronizing the ADS131M0x
    1. 4.1 The SYNC/RESET pin on the ADS131M0x
    2. 4.2 The importance of routing the clock signal
      1. 4.2.1 Single Clock Buffer
      2. 4.2.2 Multiple Clock Buffers
  8. 5Summary
  9. 6References

1 Introduction

Accurate power measurements in energy metering, motor control, and power quality monitoring systems require precise phase alignment between voltage and current channels. Measurement hardware such as current transformers (CTs), signal conditioning circuits, or ADC timing mismatches can introduce a phase error between these channels, corrupting power calculations.

The ADS131M0x is a 2-, 3-, 4-, 6-, and 8-channel, simultaneous-sampling, 24-bit delta-sigma ADC family designed for accurate power measurements. Two key features address phase error in ADS131M0x-based systems:

  • Phase compensation - the PHASEn[9:0] bits in the CHn_CFG register apply a programmable phase shift per channel, compensating for phase errors introduced by external measurement hardware.

  • Multi-device synchronization - higher channel count systems requiring multiple ADS131M0x devices introduce an additional unknown phase shift between devices, even when sharing the same clock source. Simultaneously pulsing the SYNC/RESET pin on all devices eliminates this inter-device phase shift, establishing a common time reference for simultaneous conversions.

This application note explains the sources and impact of phase error, demonstrates how to use the phase compensation feature of the ADS131M08, and describes how to synchronize multiple ADS131M0x devices to eliminate inter-device phase shifts.