SPRACZ0A August   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 , TMS320F28P550SJ , TMS320F28P550SJ , TMS320F28P559SJ-Q1 , TMS320F28P559SJ-Q1 , TMS320F28P650DH , TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P650SK , TMS320F28P659DK-Q1 , TMS320F28P659DK-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Resources
      1. 1.1.1 TINA-TI SPICE-Based Analog Simulation Program
      2. 1.1.2 PSPICE for TI Design and Simulation Tool
      3. 1.1.3 Application Report: ADC Input Circuit Evaluation for C2000 MCUs
      4. 1.1.4 TI Precision Labs - SAR ADC Input Driver Design Series
      5. 1.1.5 Analog Engineer's Calculator
      6. 1.1.6 TI Precision Labs - Op Amps: Stability Series
      7. 1.1.7 Related Application Reports
      8. 1.1.8 Comparison of Schematic Capture and Simulation Tools
      9. 1.1.9 PSpice for TI ADC Input Models
  4. 2Charge-Sharing Concept
    1. 2.1 Traditional High-Speed ADC Driving Circuits
    2. 2.2 Increased Cs in High-Speed ADC Driving Circuits
    3. 2.3 Very Large Cs in ADC Driving Circuits
    4. 2.4 Charge-Sharing Operation
    5. 2.5 Sample Rate and Source Impedance vs. Tracking Error
    6. 2.6 Analytical Solution to Tracking Error
    7. 2.7 Charge-Sharing in Multiplexed ADCs
    8. 2.8 Charge-Sharing Circuit Advantages
    9. 2.9 Charge-Sharing Circuit Disadvantages
  5. 3Charge Sharing Design Flow
    1. 3.1 Gather Required Information
    2. 3.2 Size Cs
    3. 3.3 Verify Sample Rate, Source Impedance, and Bandwidth
    4. 3.4 Simulate Circuit Settling Performance
    5. 3.5 Input Design Worksheet
  6. 4Charge-Sharing Circuit Simulation Methods
    1. 4.1 Simulation Components
      1. 4.1.1 Vin
      2. 4.1.2 Voa , Voa_SS, and Verror
      3. 4.1.3 Rs, Cs, and Vcont
      4. 4.1.4 Ch, Ron, and Cp
      5. 4.1.5 S+H Switch, Discharge Switch, tacq, and tdis
    2. 4.2 Configure the Simulation Parameters
    3. 4.3 Bias Point Analysis to Determine Voa_ss
    4. 4.4 Transient Analysis to Determine Voa_ss
    5. 4.5 Measure the Settling Error
    6. 4.6 Sweeping Source Resistance
  7. 5Example Circuit Designs
    1. 5.1 Example 1: Determining Maximum Sample Rate
      1. 5.1.1 Example 1: Analysis
      2. 5.1.2 Example 1: Simulation
      3. 5.1.3 Example 1: Worksheet
    2. 5.2 Example 2: Adding an Op-amp
      1. 5.2.1 Example 2: Analysis
      2. 5.2.2 Example 2: Simulation
      3. 5.2.3 Example 2: Worksheet
    3. 5.3 Example 3: Reduced Settling Target
      1. 5.3.1 Example 3: Analysis
      2. 5.3.2 Example 3: Simulation
      3. 5.3.3 Example 3: Worksheet
    4. 5.4 Example 4: Voltage Divider
      1. 5.4.1 Example 4: Analysis
      2. 5.4.2 Example 4: Simulation
      3. 5.4.3 Example 4: Worksheet
  8. 6Summary
  9.   A Appendix: ADC Input Settling Motivation
    1.     A.1 Mechanism of ADC Input Settling
    2.     A.2 Symptoms of Inadequate Settling
      1.      A.2.1 Distortion
      2.      A.2.2 Memory Cross-Talk
      3.      A.2.3 Accuracy
      4.      A.2.4 C2000 ADC Architecture
  10.   References
  11.   Revision History

4.1.3 Rs, Cs, and Vcont

Rs and Cs are the source resistance and source capacitance. These values correspond to Rfilt and Cfilt in the TI Precision Labs training terminology. Rs resistance is determined by the global parameter R_STEP. Using a global parameter allows parameter sweeping when there are two Rs resistors in the differential models.