SBAA487 January   2021 ADS8664 , ADS8668 , ADS8674 , ADS8678 , ADS8684 , ADS8684A , ADS8686S , ADS8688 , ADS8688A , ADS8694 , ADS8698

 

  1.   Trademarks
  2. 1Introduction
  3. 2Phase Delay and Non-Simultaneous Sampling
  4. 3Averaging with Sequencer and Burst Sequencer mode
    1. 3.1 Averaging with Sequencer
    2. 3.2 Averaging with Burst Sequencer
  5. 4Verification and Measured Result
    1. 4.1 Phase Delay Measurement
      1. 4.1.1 Measured Phase Delay without Averaging – 50Hz Sinusoidal Fundamental Signal
      2. 4.1.2 Measured Phase Delay with Averaging – 50Hz sinusoidal fundamental signal
      3. 4.1.3 Comparison
    2. 4.2 AC Performance
  6. 5Summary
  7. 6References

1 Introduction

In a grid infrastructure application, measuring the phase difference between different signals is critical to ensure the safety of the power grid. The simultaneous sampling, multiple-channels inputs analog-to-digital converter (ADC) is ideal for the kind of application. However, to reduce the channel count and the cost, a non-simultaneous sampling, multiple-channels inputs ADC with internal multiplexer can be used.

When multiple input channels are sampled in a sequential manner as in a multiplexed ADC, an additional phase delay is introduced between the channels because of channel switching. The measured phase value of the signal includes this additional phase delay which is not expected by the design engineer and will lead to an inaccurate phase difference measurement. The reference design of Phase-Compensated, 8-Ch, Multiplexed Data Acquisition System for Power Automation Reference Design introduces a method how to compensate the additional phase delay caused by the channel switching on the internal multiplexer.

ADS8686S is a 16-channel, 16-bit, 1Msps, Dual simultaneous sampling successive approximation register (SAR) based ADC, the integrated analog front-end (AFE) with 1MΩ input impedance eliminates the requirement of ADC driver. The 16-channel inputs can meet the requirement in most multi-phase power measurement systems and make it possible to design a compact system. However, the channel switching on each ADC A/B of ADS8686S will introduce an additional phase delay.

GUID-20210105-CA0I-BF4N-2VB2-J4HX2L74RZJ4-low.gif Figure 1-1 Typical Application Circuit Using ADS8686S in Grid Infrastructure System