TIDUF13 November   2022 ADS117L11 , ADS127L11

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specification
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Signal-Chain Voltage Levels
        1.       12
      2. 2.2.2 ADC Configuration
      3. 2.2.3 ADC Clocking and Synchronization
      4. 2.2.4 Differential Low-Pass Filter
      5. 2.2.5 Current Source
      6. 2.2.6 Gain Stage and High-Pass Filter
    3. 2.3 Highlighted Products
      1. 2.3.1 ADS127L11
      2. 2.3.2 THS4551
  8. 3System Design Theory
    1. 3.1 IEPE Sensor
      1. 3.1.1 IEPE Sensor Parameters
        1. 3.1.1.1 Sensitivity and Measurement Range
        2. 3.1.1.2 Excitation, Output Bias Voltage, and Output Impedance
        3. 3.1.1.3 Linearity and Temperature Variance
        4. 3.1.1.4 Frequency Response
        5. 3.1.1.5 Noise and Dynamic Range
  9. 4Hardware, Software, Testing, and Test Results
    1. 4.1 Hardware Description
      1. 4.1.1 Board Interface
      2. 4.1.2 Power Configuration
        1. 4.1.2.1 Power Sequence
        2. 4.1.2.2 Analog Supply
        3. 4.1.2.3 Digital Supply
        4. 4.1.2.4 Excitation Current Supply
        5. 4.1.2.5 SPI Connectivity Modes and Their Assembly Variants
          1. 4.1.2.5.1 Daisy-Chain Mode
          2. 4.1.2.5.2 Parallel SDO Mode
          3. 4.1.2.5.3 Parallel SDI Mode and Parallel SDO Mode
          4. 4.1.2.5.4 Clocking Modes
    2. 4.2 Software Requirements
    3. 4.3 Test Setup and Procedure
      1. 4.3.1 Noise Floor and SNR
      2. 4.3.2 Gain and Input Range
      3. 4.3.3 Crosstalk
      4. 4.3.4 Total Harmonic Distortion
      5. 4.3.5 Clock Image Rejection
      6. 4.3.6 Synchronization of the ADCs
      7. 4.3.7 Fault Detection Circuit
    4. 4.4 Test Results
      1. 4.4.1 Noise Floor and Dynamic Range
      2. 4.4.2 Gain and Input Range
      3. 4.4.3 Crosstalk
      4. 4.4.4 Total Harmonic Distortion
      5. 4.4.5 Clock Image Rejection
      6. 4.4.6 Synchronization of the ADCs
      7. 4.4.7 Fault Detection Circuit
      8. 4.4.8 Test With Actual IEPE Sensor
      9. 4.4.9 Measurement Results Summary
  10. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  11. 6About the Author

4.3.2 Gain and Input Range

For evaluation of signal-chain gain an input range without excitation current or actual sensors, use the following setup:

  • Connect the input source to pins (2, 3) of J8A, a low distortion source capable of ±10-V output is recommended, such as R&S Audio Analyzer UPD with THD < –100 dB
  • set the output of the source to maximum level Vp-p = 20V, low frequency like 100 Hz
  • Capture the ADC time domain and calculate gain (from peak-to-peak value)
  • Set the source frequency to 18 kHz and calculate the gain by capturing the ADC output again
  • The previous steps can be repeated over different frequencies to draw the frequency response of the channel
  • To test channel #4, make sure the attenuator common mode is connected to the ADC common mode. Short J13 (1,2 , right side).
  • If required, a differential signal at the input of the ADC can be measured using a differential probe through the test points just before the ADC inputs

Make sure no clipping appears in the signal to verify the signal chain is properly biased.