SPRACY9 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 , TMS320F28P650DH , TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P650SK , TMS320F28P659DH-Q1 , TMS320F28P659DH-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659SH-Q1 , TMS320F28P659SH-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Mechanism of ADC Input Settling
    2. 1.2 Symptoms of Inadequate Settling
      1. 1.2.1 Distortion
      2. 1.2.2 Memory Cross-Talk
      3. 1.2.3 Accuracy
      4. 1.2.4 C2000 ADC Architecture
    3. 1.3 Resources
      1. 1.3.1 TINA-TI SPICE-Based Analog Simulation Program
      2. 1.3.2 PSPICE for TI Design and Simulation Tool
      3. 1.3.3 TI Precision Labs - SAR ADC Input Driver Design Series
      4. 1.3.4 Analog Engineer's Calculator
      5. 1.3.5 Related Application Reports
      6. 1.3.6 PSpice for TI ADC Input Models
  4. 2Input Settling Design Steps
    1. 2.1 Select the ADC
    2. 2.2 Find the Minimum Op-Amp Bandwidth and RC Filter Ranges
      1. 2.2.1 Select Type
      2. 2.2.2 Resolution
      3. 2.2.3 Csh
      4. 2.2.4 Full-Scale Range
      5. 2.2.5 Acquisition Time
      6. 2.2.6 Outputs
      7. 2.2.7 Math Behind the Calculator
    3. 2.3 Select an Op-Amp
    4. 2.4 Verify the Op-Amp Model
    5. 2.5 Build the ADC Input Model
      1. 2.5.1 Vin
      2. 2.5.2 Voa, Voa_SS, and Verror
      3. 2.5.3 Rs, Cs, and Vcont
      4. 2.5.4 Ch, Ron, and Cp
      5. 2.5.5 S+H Switch, Discharge Switch, tacq, and tdis
    6. 2.6 Refine RC Filter Values Via Simulation
    7. 2.7 Perform Final Simulations
    8. 2.8 Input Design Worksheet
  5. 3Example Circuit Design
    1. 3.1  Select the ADC
    2. 3.2  Find the Minimum Op-Amp Bandwidth and RC Filter Ranges
    3. 3.3  Verify the Op-Amp Model
    4. 3.4  Build the ADC Input Model
    5. 3.5  Bias Point Analysis to Determine Voa_ss
    6. 3.6  Transient Analysis to Determine Voa_ss
    7. 3.7  Perform Initial Transient Analysis
    8. 3.8  Iterative Approach to Refine RC Filter Values
    9. 3.9  Perform Final Transient Analysis
    10. 3.10 Perform Final Transient Analysis
    11. 3.11 Further Refinement
    12. 3.12 Further Simulations
    13. 3.13 Completed Worksheet
  6. 4Working With Existing Circuits or Additional Constraints
    1. 4.1 Existing Circuits
      1. 4.1.1 Brief Overview of Charge Sharing
      2. 4.1.2 Charge Sharing Example
      3. 4.1.3 Additional Resources for Charge Sharing
    2. 4.2 Pre-Selected Op-Amp
      1. 4.2.1 Pre-Selected Op-Amp Example
    3. 4.3 Pre-Selected Rs and Cs Values
      1. 4.3.1 Analytical Solution for ADC Acquisition Time
      2. 4.3.2 Example Analytical Solution for ADC Acquisition Time
  7. 5Summary
  8. 6References

2.1 Select the ADC

It is assumed that you have already selected a C28x based microcontroller with one or more integrated ADC modules. The C28x product search can be used to select an MCU: C2000 real-time control MCU - Products and the C2000 peripheral guide enumerates the differences between peripherals on different devices (including the ADC): C2000 Real-Time Control MCU Peripherals Reference Guide.

Once a C2000 device has been selected, you should locate the following information in the device-specific data manual before proceeding.

Data Manual InformationLocationComments
Minimum sample window duration"ADC Operating Conditions" table in the "ADC Electrical Data and Timing" sectionSome devices support multiple resolution modes and signaling modes; ensure that the parameter corresponds to the mode you intend to use.
ADC input model"Input Model Parameters" table in the "ADC Input Model" sectionSome devices support multiple resolution modes and signaling modes; ensure that the model corresponds to the mode you intend to use.
Specific parasitic capacitance for selected ADC pin"Per-Channel Parasitic Capacitance" table in the "ADC Input Model" sectionIf channel assignment is not yet known, use the value for ADCIN15.
ADC timings"ADC Timings" table in the "ADC Timing Diagrams" sectionSome devices support multiple resolution modes and signaling modes; ensure that the timings correspond to the mode you intend to use. You will also need to know your intended CPU clock (SYSCLK) and ADC clock (ADCCLK) rate. If not yet known, use the maximum ADCCLK value given in the "ADC Operating Conditions" table along with the maximum SYSCLK for the device.