SBAS444E May   2009  – December 2024

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5.   Device Comparison Table
  6. 4 Pin Configuration and Functions
  7. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements: I2C
    7. 5.7 Typical Characteristics
  8. 6 Parameter Measurement Information
    1. 6.1 Noise Performance
  9. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Multiplexer
      2. 7.3.2 Analog Inputs
      3. 7.3.3 Full-Scale Range (FSR) and LSB Size
      4. 7.3.4 Voltage Reference
      5. 7.3.5 Oscillator
      6. 7.3.6 Output Data Rate and Conversion Time
      7. 7.3.7 Digital Comparator (ADS1114 and ADS1115 Only)
      8. 7.3.8 Conversion Ready Pin (ADS1114 and ADS1115 Only)
      9. 7.3.9 SMbus Alert Response
    4. 7.4 Device Functional Modes
      1. 7.4.1 Reset and Power-Up
      2. 7.4.2 Operating Modes
        1. 7.4.2.1 Single-Shot Mode
        2. 7.4.2.2 Continuous-Conversion Mode
      3. 7.4.3 Duty Cycling For Low Power
    5. 7.5 Programming
      1. 7.5.1 I2C Interface
        1. 7.5.1.1 I2C Address Selection
        2. 7.5.1.2 I2C General Call
        3. 7.5.1.3 I2C Speed Modes
      2. 7.5.2 Target Mode Operations
        1. 7.5.2.1 Receive Mode
        2. 7.5.2.2 Transmit Mode
      3. 7.5.3 Writing To and Reading From the Registers
      4. 7.5.4 Data Format
  10. 8 Registers
    1. 8.1 Register Map
      1. 8.1.1 Address Pointer Register (address = N/A) [reset = N/A]
      2. 8.1.2 Conversion Register (P[1:0] = 00b) [reset = 0000h]
      3. 8.1.3 Config Register (P[1:0] = 01b) [reset = 8583h]
      4. 8.1.4 Lo_thresh (P[1:0] = 10b) [reset = 8000h] and Hi_thresh (P[1:0] = 11b) [reset = 7FFFh] Registers
  11. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Basic Connections
      2. 9.1.2 Single-Ended Inputs
      3. 9.1.3 Input Protection
      4. 9.1.4 Unused Inputs and Outputs
      5. 9.1.5 Analog Input Filtering
      6. 9.1.6 Connecting Multiple Devices
      7. 9.1.7 Quick-Start Guide
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Shunt Resistor Considerations
        2. 9.2.2.2 Operational Amplifier Considerations
        3. 9.2.2.3 ADC Input Common-Mode Considerations
        4. 9.2.2.4 Resistor (R1, R2, R3, R4) Considerations
        5. 9.2.2.5 Noise and Input Impedance Considerations
        6. 9.2.2.6 First-Order RC Filter Considerations
        7. 9.2.2.7 Circuit Implementation
        8. 9.2.2.8 Results Summary
      3. 9.2.3 Application Curves
  12. 10Power Supply Recommendations
    1. 10.1 Power-Supply Sequencing
    2. 10.2 Power-Supply Decoupling
  13. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  14. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  15. 13Revision History
  16. 14Mechanical, Packaging, and Orderable Information

9.2.2.3 ADC Input Common-Mode Considerations

VCM sets the VOUT common-mode voltage by appropriate selection of precision resistors R1, R2, R3, and R4.

If R1 = R3, R2 = R4, and VSHUNT = 0V, VOUT is given by Equation 10.

Equation 10. VOUT = VCM

If VOUT is connected to the ADC positive input (AINP) and VCM is connected to the ADC negative input (AINN), VCM appears as a common-mode voltage to the ADC. This configuration allows pseudo-differential measurements and uses the maximum dynamic range of the ADC if VCM is set at mid-supply (VDD / 2). A resistor divider from VDD to GND followed by a buffer amplifier can be used to generate VCM.