SPRACW9A June   2021  – March 2023 TMS320F2800132 , TMS320F2800132 , TMS320F2800133 , TMS320F2800133 , TMS320F2800135 , TMS320F2800135 , TMS320F2800137 , TMS320F2800137 , TMS320F2800152-Q1 , TMS320F2800152-Q1 , TMS320F2800153-Q1 , TMS320F2800153-Q1 , TMS320F2800154-Q1 , TMS320F2800154-Q1 , TMS320F2800155 , TMS320F2800155 , TMS320F2800155-Q1 , TMS320F2800155-Q1 , TMS320F2800156-Q1 , TMS320F2800156-Q1 , TMS320F2800157 , TMS320F2800157 , TMS320F2800157-Q1 , TMS320F2800157-Q1 , TMS320F280021 , TMS320F280021 , TMS320F280021-Q1 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280023C , TMS320F280025 , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280025C-Q1 , TMS320F280033 , TMS320F280033 , TMS320F280034 , TMS320F280034 , TMS320F280034-Q1 , TMS320F280034-Q1 , TMS320F280036-Q1 , TMS320F280036-Q1 , TMS320F280036C-Q1 , TMS320F280036C-Q1 , TMS320F280037 , TMS320F280037 , TMS320F280037-Q1 , TMS320F280037-Q1 , TMS320F280037C , TMS320F280037C , TMS320F280037C-Q1 , TMS320F280037C-Q1 , TMS320F280038-Q1 , TMS320F280038-Q1 , TMS320F280038C-Q1 , TMS320F280038C-Q1 , TMS320F280039 , TMS320F280039 , TMS320F280039-Q1 , TMS320F280039-Q1 , TMS320F280039C , TMS320F280039C , TMS320F280039C-Q1 , TMS320F280039C-Q1 , TMS320F280040-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C , TMS320F280049C-Q1 , TMS320F280049C-Q1 , TMS320F28075 , TMS320F28075 , TMS320F28075-Q1 , TMS320F28075-Q1 , TMS320F28076 , TMS320F28076 , TMS320F28374D , TMS320F28374D , TMS320F28374S , TMS320F28374S , TMS320F28375D , TMS320F28375D , TMS320F28375S , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28375S-Q1 , TMS320F28376D , TMS320F28376D , TMS320F28376S , TMS320F28376S , TMS320F28377D , TMS320F28377D , TMS320F28377D-EP , TMS320F28377D-EP , TMS320F28377D-Q1 , TMS320F28377D-Q1 , TMS320F28377S , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28377S-Q1 , TMS320F28378D , TMS320F28378D , TMS320F28378S , TMS320F28378S , TMS320F28379D , TMS320F28379D , TMS320F28379D-Q1 , TMS320F28379D-Q1 , TMS320F28379S , TMS320F28379S , TMS320F28384D , TMS320F28384D , TMS320F28384D-Q1 , TMS320F28384D-Q1 , TMS320F28384S , TMS320F28384S , TMS320F28384S-Q1 , TMS320F28384S-Q1 , TMS320F28386D , TMS320F28386D , TMS320F28386D-Q1 , TMS320F28386D-Q1 , TMS320F28386S , TMS320F28386S , TMS320F28386S-Q1 , TMS320F28386S-Q1 , TMS320F28388D , TMS320F28388D , TMS320F28388S , TMS320F28388S , TMS320F28P650DK , TMS320F28P650DK , TMS320F28P659DK-Q1 , TMS320F28P659DK-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Memory Cross-Talk Challenges
    2. 1.2 Resources for Signal Conditioning Circuit Design
      1. 1.2.1 TI Precision Labs - SAR ADC Input Driver Design Series
      2. 1.2.2 Analog Engineer's Calculator
      3. 1.2.3 Related Application Reports
      4. 1.2.4 TINA-TI SPICE-Based Analog Simulation Program
      5. 1.2.5 PSPICE for TI
      6. 1.2.6 ADC Input Circuit Evaluation for C2000 MCUs
      7. 1.2.7 Charge-Sharing Driving Circuits for C2000 ADCs
  4. 2Review of ADC Input Settling
    1. 2.1 Mechanism of ADC Input Settling
    2. 2.2 Symptoms of Inadequate Settling
      1. 2.2.1 Distortion
      2. 2.2.2 Memory Cross-Talk
      3. 2.2.3 Accuracy
    3. 2.3 C2000 ADC Architecture
  5. 3Problem Statement
    1. 3.1 Example System
    2. 3.2 S+H Settling Analysis
    3. 3.3 Charge-Sharing Analysis
    4. 3.4 Problem Summary
  6. 4Dedicated ADC Sampling
    1. 4.1 Dedicated ADC Concept
    2. 4.2 Settling Mechanism for Dedicated ADC
    3. 4.3 Design Flow for Dedicated ADC
    4. 4.4 Simulating Settling Performance for a Dedicated ADC Circuit
  7. 5Pre-Sampling VREFLO
    1. 5.1 VREFLO Sampling Concept
    2. 5.2 Properties of VREFLO Sampling Method Error
    3. 5.3 Gain Error Compensation
      1. 5.3.1 Methods for Determining Compensation Coefficients
    4. 5.4 VREFLO Sampling Design Flow
    5. 5.5 Discussion of VREFLO Sampling Sequences
  8. 6Summary
  9. 7References
  10. 8Revision History

Abstract

High-speed multiplexed analog-to-digital converters (ADCs) like those found on C2000™ series microcontrollers enable fast sensing of multiple feedback signals in real-time control applications. The signal conditioning circuits for these feedback signals should be carefully designed and evaluated to ensure that adequate settling is achieved in the time allocated for the ADC's sample-and-hold (S+H). In cases where adequate settling is not achieved in the hardware design of the signal conditioning circuits, memory cross-talk issues can arise in the system. This application report reviews the causes and symptoms of memory cross-talk and then presents two possible strategies for mitigating the memory cross-talk error: dedicating an ADC to the affected signal (resulting in only self cross-talk) and sampling ground before the affected signal (transforming the memory cross-talk into a gain error, which can subsequently be calibrated out of the system).

Project collateral discussed in this document can be downloaded from the following URL: https://www.ti.com/lit/zip/spracw9.