SBAS535D August   2013  – June 2026 ADS1120

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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 SPI Timing Requirements
    7. 6.7 SPI Switching Characteristics
    8. 6.8 Timing Diagrams
    9. 6.9 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Noise Performance
  9. 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  Low-Noise PGA
        1. 8.3.2.1 PGA Common-Mode Voltage Requirements
        2. 8.3.2.2 Bypassing the PGA
      3. 8.3.3  Voltage Reference
      4. 8.3.4  Clock Source
      5. 8.3.5  Modulator
      6. 8.3.6  Digital Filter
      7. 8.3.7  Output Data Rate
      8. 8.3.8  Excitation Current Sources
      9. 8.3.9  Low-Side Power Switch
      10. 8.3.10 Sensor Detection
      11. 8.3.11 System Monitor
      12. 8.3.12 Offset Calibration
      13. 8.3.13 Temperature Sensor
        1. 8.3.13.1 Converting From Digital Codes to Temperature
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Up and Reset
      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 Operating Modes
        1. 8.4.3.1 Normal Mode
        2. 8.4.3.2 Duty-Cycle Mode
        3. 8.4.3.3 Turbo Mode
        4. 8.4.3.4 Power-Down Mode
    5. 8.5 Programming
      1. 8.5.1 Serial Interface
        1. 8.5.1.1 Chip Select (CS)
        2. 8.5.1.2 Serial Clock (SCLK)
        3. 8.5.1.3 Data Ready (DRDY)
        4. 8.5.1.4 Data Input (DIN)
        5. 8.5.1.5 Data Output and Data Ready (DOUT/DRDY)
        6. 8.5.1.6 SPI Timeout
      2. 8.5.2 Data Format
      3. 8.5.3 Commands
        1. 8.5.3.1 RESET (0000 011xb)
        2. 8.5.3.2 START/SYNC (0000 100xb)
        3. 8.5.3.3 POWERDOWN (0000 001xb)
        4. 8.5.3.4 RDATA (0001 xxxxb)
        5. 8.5.3.5 RREG (0010 rrnnb)
        6. 8.5.3.6 WREG (0100 rrnnb)
      4. 8.5.4 Reading Data
      5. 8.5.5 Sending Commands
      6. 8.5.6 Interfacing with Multiple Devices
    6. 8.6 Register Map
      1. 8.6.1 Configuration Registers
      2. 8.6.2 Register Descriptions
        1. 8.6.2.1 Configuration Register 0 (Address = 00h) [reset = 00h]
        2. 8.6.2.2 Configuration Register 1 (Address = 01h) [reset = 00h]
        3. 8.6.2.3 Configuration Register 2 (Address = 02h) [reset = 00h]
        4. 8.6.2.4 Configuration Register 3 (Address = 03h) [reset = 00h]
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Serial Interface Connections
      2. 9.1.2 Analog Input Filtering
      3. 9.1.3 External Reference and Ratiometric Measurements
      4. 9.1.4 Establishing a Proper Common-Mode Input Voltage
      5. 9.1.5 Unused Inputs and Outputs
      6. 9.1.6 Pseudo Code Example
    2. 9.2 Typical Applications
      1. 9.2.1 K-Type Thermocouple Measurement (–200°C to +1250°C)
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 3-Wire RTD Measurement (–200°C to +850°C)
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Design Variations for 2-Wire and 4-Wire RTD Measurements
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Resistive Bridge Measurement
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Power-Supply Sequencing
      2. 9.3.2 Power-Supply Ramp Rate
      3. 9.3.3 Power-Supply Decoupling
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

8.1 Overview

The ADS1120 is a small, low-power, 16-bit, ΔΣ ADC that offers many integrated features to reduce system cost and component count in applications measuring small sensor signals.

In addition to the ΔΣ ADC core and single-cycle settling digital filter, the device offers a low-noise, high input impedance, programmable gain amplifier (PGA), an internal voltage reference, and a clock oscillator. The device also integrates a highly linear and accurate temperature sensor as well as two matched programmable current sources (IDACs) for sensor excitation. All of these features are intended to reduce the required external circuitry in typical sensor applications and improve overall system performance. An additional low-side power switch eases the design of low-power bridge sensor applications. The device is fully configured through four registers and controlled by six commands through a mode 1 SPI-compatible interface. The Functional Block Diagram section shows the device functional block diagram.

The ADS1120 ADC measures a differential signal, VIN, which is the difference in voltage between nodes AINP and AINN. The converter core consists of a differential, switched-capacitor, ΔΣ modulator followed by a digital filter. The digital filter receives a high-speed bitstream from the modulator and outputs a code proportional to the input voltage. This architecture results in a very strong attenuation of any common-mode signal.

The device has two available conversion modes: single-shot and continuous conversion mode. In single-shot conversion mode, the ADC performs one conversion of the input signal upon request and stores the value in an internal data buffer. The device then enters a low-power state to save power. Single-shot conversion mode is intended to provide significant power savings in systems that require only periodic conversions, or when there are long idle periods between conversions. In continuous conversion mode, the ADC automatically begins a conversion of the input signal as soon as the previous conversion is completed. New data are available at the programmed data rate. Data can be read at any time without concern of data corruption and always reflect the most recently completed conversion.