SBAS924A July   2018  – November 2018 ADS1219

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Voltage, Current, and Temperature Monitoring Application
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 I2C Timing Requirements
    7. 6.7 I2C Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Noise Performance
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Multiplexer
      2. 8.3.2 Rail-to-Rail Input Buffers and Programmable Gain Stage
      3. 8.3.3 Voltage Reference
      4. 8.3.4 Modulator and Internal Oscillator
      5. 8.3.5 Digital Filter
      6. 8.3.6 Conversion Times
      7. 8.3.7 Offset Calibration
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Up and Reset
        1. 8.4.1.1 Power-On Reset
        2. 8.4.1.2 RESET Pin
        3. 8.4.1.3 Reset by Command
      2. 8.4.2 Conversion Modes
        1. 8.4.2.1 Single-Shot Conversion Mode
        2. 8.4.2.2 Continuous Conversion Mode
      3. 8.4.3 Power-Down Mode
    5. 8.5 Programming
      1. 8.5.1 I2C Interface
        1. 8.5.1.1 I2C Address
        2. 8.5.1.2 Serial Clock (SCL) and Serial Data (SDA)
        3. 8.5.1.3 Data Ready (DRDY)
        4. 8.5.1.4 Interface Speed
        5. 8.5.1.5 Data Transfer Protocol
        6. 8.5.1.6 I2C General Call (Software Reset)
        7. 8.5.1.7 Timeout
      2. 8.5.2 Data Format
      3. 8.5.3 Commands
        1. 8.5.3.1 Command Latching
        2. 8.5.3.2 RESET (0000 011x)
        3. 8.5.3.3 START/SYNC (0000 100x)
        4. 8.5.3.4 POWERDOWN (0000 001x)
        5. 8.5.3.5 RDATA (0001 xxxx)
        6. 8.5.3.6 RREG (0010 0rxx)
        7. 8.5.3.7 WREG (0100 00xx dddd dddd)
      4. 8.5.4 Reading Data and Monitoring for New Conversion Results
    6. 8.6 Register Map
      1. 8.6.1 Configuration and Status Registers
      2. 8.6.2 Register Descriptions
        1. 8.6.2.1 Configuration Register (address = 0h) [reset = 00h]
          1. Table 10. Configuration Register Field Descriptions
        2. 8.6.2.2 Status Register (address = 1h) [reset = 00h]
          1. Table 11. Status Register Field Descriptions
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Interface Connections
      2. 9.1.2 Connecting Multiple Devices on the Same I2C Bus
      3. 9.1.3 Unused Inputs and Outputs
      4. 9.1.4 Analog Input Filtering
      5. 9.1.5 External Reference and Ratiometric Measurements
      6. 9.1.6 Establishing Proper Limits on the Absolute Input Voltage
      7. 9.1.7 Pseudo Code Example
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Voltage Monitoring
        2. 9.2.2.2 High-Side Current Measurement
        3. 9.2.2.3 Thermistor Measurement
        4. 9.2.2.4 Register Settings
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
    1. 10.1 Power-Supply Sequencing
    2. 10.2 Power-Supply Decoupling
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.2.2.1 Voltage Monitoring

The ADS1219 can measure single-ended signals ranging from AGND to VREF / Gain. In order to monitor voltages up to 2 V, the device is configured to use the internal 2.048-V reference and gain = 1.

Equation 6 details the relationship between output codes of the ADS1219 and the input voltage on AIN3.

Equation 6. VAIN3 = (VREF / Gain) · (Code / 223) = 2.048 V · Code / 223

An external voltage reference must be provided on the external reference inputs of the device in case larger voltages than 2.048 V are to be monitored. The device can measure input signals up to the positive analog supply voltage in case AVDD is used as the positive reference input (REFP) and AGND as the negative reference input (REFN). However the ADS1219 cannot monitor its own supply voltage in that case. As described in Equation 6, when using VAIN3 = AVDD and VREF = AVDD, the device will always output a positive full-scale code irrespective of the value of AVDD. To monitor the supply of the ADC, use a resistor divider instead to divide the supply voltage down to below 2.048 V and measure the voltage using the internal reference.

The input-referred peak-to-peak noise of the ADC is ideally a factor smaller than the required measurement accuracy of ±0.5 mV. At 90 SPS using gain = 1 the ADS1219 offers an input-referred noise of 43 µVPP, which meets this requirement.