TIDUFC1 November   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 ADS127L21B
      2. 2.3.2 REF81
      3. 2.3.3 REF54
      4. 2.3.4 RES21A
      5. 2.3.5 THP210
      6. 2.3.6 OPA828
  9. 3System Design Theory
    1. 3.1 Range Selection
    2. 3.2 Linearity and Low-Noise Signal Chain
    3. 3.3 Calibration
    4. 3.4 Additional System Design Considerations
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Description
      1. 4.1.1 PCB Interface
      2. 4.1.2 Input Multiplexer
      3. 4.1.3 Gain Multiplexer
      4. 4.1.4 Power Supplies
      5. 4.1.5 Clock Tree
    2. 4.2 Software Requirements
    3. 4.3 Test Setup
    4. 4.4 Test Results
      1. 4.4.1 Integral Nonlinearity Measurements
      2. 4.4.2 Noise Simulation
      3. 4.4.3 Noise Measurements
      4. 4.4.4 Conclusion
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Tools
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

4.1.3 Gain Multiplexer

Select the desired input range using the 4-channel gain multiplexer (U7). The gain multiplexer changes the input amplifier (U4) gain. The input signal needs to be scaled to the ADS127L21B full-scale range to maximize measurement resolution. The input amplifier scales the input signal to a 10V scale. Jumpers J11, J12, and J13 enable the gain multiplexer and select the desired input channel. See Table 4-3 for more details.

Table 4-3 Jumper Settings for Gain Multiplexer
J11 (En)J12 (A1)J13 (A0)INPUT CHANNELVOLTAGE RANGE
0X(1)X(1)U7 Disabled–
10X(1)Gain = 1.00V/V±10V
110Gain = 10.0V/V±1V
111Gain = 99.8V/V±100mV
(1) 'X' denotes a 'Don't Care'.
TIDA-010970 Gain Multiplexer SchematicFigure 4-4 Gain Multiplexer Schematic