SBASAI9 December   2025 ADS122S14

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 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
    7. 5.7 Switching Characteristics
    8. 5.8 Timing Diagrams
    9. 5.9 Typical Characteristics
  7. 6 Parameter Measurement Information
    1. 6.1 Noise Performance
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Analog Inputs and Multiplexer
      2. 7.3.2  Programmable Gain Amplifier (PGA)
      3. 7.3.3  Voltage Reference
        1. 7.3.3.1 Internal Reference
        2. 7.3.3.2 External Reference
        3. 7.3.3.3 Reference Buffers
      4. 7.3.4  Clock Source
      5. 7.3.5  Delta-Sigma Modulator
      6. 7.3.6  Digital Filter
        1. 7.3.6.1 Sinc4 and Sinc4 + Sinc1 Filter
        2. 7.3.6.2 FIR Filter
        3. 7.3.6.3 Digital Filter Latency
        4. 7.3.6.4 Global-Chop Mode
      7. 7.3.7  Excitation Current Sources (IDACs)
      8. 7.3.8  Burn-Out Current Sources (BOCS)
      9. 7.3.9  General Purpose IOs (GPIOs)
        1. 7.3.9.1 FAULT Output
        2. 7.3.9.2 DRDY Output
      10. 7.3.10 System Monitors
        1. 7.3.10.1 Internal Short (Offset Calibration)
        2. 7.3.10.2 Internal Temperature Sensor
        3. 7.3.10.3 External Reference Voltage Readback
        4. 7.3.10.4 Power-Supply Readback
      11. 7.3.11 Monitors and Status Flags
        1. 7.3.11.1 Reset (RESETn flag)
        2. 7.3.11.2 AVDD Undervoltage Monitor (AVDD_UVn flag)
        3. 7.3.11.3 Reference Undervoltage Monitor (REV_UVn flag)
        4. 7.3.11.4 SPI CRC Fault (SPI_CRC_FAULTn flag)
        5. 7.3.11.5 Register Map CRC Fault (REG_MAP_CRC_FAULTn flag)
        6. 7.3.11.6 Internal Memory Fault (MEM_FAULTn flag)
        7. 7.3.11.7 Register Write Fault (REG_WRITE_FAULTn flag)
        8. 7.3.11.8 DRDY Indicator (DRDY bit)
        9. 7.3.11.9 Conversion Counter (CONV_COUNT[3:0])
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power-up and Reset
        1. 7.4.1.1 Power-On Reset (POR)
        2. 7.4.1.2 Reset by Register Write
        3. 7.4.1.3 Reset by SPI Input Pattern
      2. 7.4.2 Operating Modes
        1. 7.4.2.1 Idle and Standby Mode
        2. 7.4.2.2 Power-Down Mode
        3. 7.4.2.3 Power-Scalable Conversion Modes
          1. 7.4.2.3.1 Continuous-Conversion Mode
          2. 7.4.2.3.2 Single-shot Conversion Mode
    5. 7.5 Programming
      1. 7.5.1  Serial Interface (SPI)
      2. 7.5.2  Serial Interface Signals
        1. 7.5.2.1 Chip Select (CS)
        2. 7.5.2.2 Serial Clock (SCLK)
        3. 7.5.2.3 Serial Data Input (SDI)
        4. 7.5.2.4 Serial Data Output/Data Ready (SDO/DRDY)
        5. 7.5.2.5 Data Ready (DRDY) Pin
      3. 7.5.3  Serial Interface Communication Structure
        1. 7.5.3.1 SPI Frame
        2. 7.5.3.2 STATUS Header
        3. 7.5.3.3 SPI CRC
      4. 7.5.4  Device Commands
        1. 7.5.4.1 No Operation (Read Conversion Data)
        2. 7.5.4.2 Read Register Command
        3. 7.5.4.3 Write Register Command
      5. 7.5.5  Continuous-Read Mode
        1. 7.5.5.1 Read Registers in Continuous-Read Mode
      6. 7.5.6  Daisy-Chain Operation
      7. 7.5.7  3-Wire SPI Mode
        1. 7.5.7.1 3-Wire SPI Mode Frame Re-Alignment
      8. 7.5.8  Monitoring for New Conversion Data
        1. 7.5.8.1 DRDY Pin or SDO/DRDY Pin Monitoring
        2. 7.5.8.2 Reading DRDY Bit and Conversion Counter
        3. 7.5.8.3 Clock Counting
      9. 7.5.9  DRDY Pin Behavior
      10. 7.5.10 Conversion Data Format
      11. 7.5.11 Register Map CRC
  9. 8 Registers
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Serial Interface Connections
      2. 9.1.2 Interfacing with Multiple Devices
      3. 9.1.3 Unused Inputs and Outputs
      4. 9.1.4 Device Initialization
    2. 9.2 Typical Applications
      1. 9.2.1 Software-Configurable RTD Measurement Input
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Performance Plots
        4. 9.2.1.4 Design Variant – 3-Wire RTD Measurement With Automatic Lead-Wire Compensation Using Two IDACs
      2. 9.2.2 Thermocouple Measurement With Cold-Junction Compensation Using a 2-wire RTD
      3. 9.2.3 Resistive Bridge Sensor Measurement With Temperature Compensation
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Power Supplies
      2. 9.3.2 Power-Supply Sequencing
      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

7.3.2 Programmable Gain Amplifier (PGA)

The ADS1x2S14 integrate a low-drift, low-noise, high input impedance programmable gain amplifier (PGA). Use the GAIN[3:0] bits to configure the PGA for gains of 0.5, 1, 2, 4, 5, 8, 10, 16, 20, 32, 50, 64, 100, 128, 200, or 256. The full-scale input voltage range (FSR) of the PGA is defined by the gain setting, the reference voltage, and the conversion data coding setting, as shown in Equation 6 and Equation 7:

Equation 6. Binary two's complement coding: FSR = ±VREF / Gain
Equation 7. Unipolar straight binary coding: FSR = 0V to +VREF / Gain

Table 7-1 shows the corresponding nominal full-scale ranges using binary two's complement coding for a 1.25V and a 2.5V reference voltage, respectively.

Table 7-1 PGA Full-Scale Range (Binary Two's Complement Coding)
GAIN SETTING VREF = 1.25V VREF = 2.5V
0.5 ±2.5V ±5V
1 ±1.25V ±2.5V
2 ±0.625V ±1.25V
4 ±0.313V ±0.625V
5 ±0.25V ±0.5V
8 ±0.156V ±0.313V
10 ±0.125V ±0.25V
16 ±78.125mV ±0.156V
20 ±62.5mV ±0.125V
32 ±39.063mV ±78.125mV
50 ±25mV ±50mV
64 ±19.531mV ±30.063mV
100 ±12.5mV ±25mV
128 ±9.766mV ±19.531mV
200 ±6.25mV ±12.5mV
256 ±4.883mV ±9.766mV

Depending on the gain setting, the PGA has certain voltage headroom requirements to stay within the linear operating range that must be met for the selected positive and negative analog inputs as specified by the absolute input voltage parameter in the Recommended Operating Conditions. Both the positive and negative PGA inputs need to stay within those voltage limits, even for FSR settings which in principle extend beyond those limits. For example, assume AVDD = 3.3V, gain = 0.5, VREF = 2.5V, unipolar coding scheme, and AINN connected to GND. In this case AINP needs to stay between 0V and (3.3V – 0.35V) = 2.95V. Therefore only a portion of the full code range (FSR = 0V to 5V) is utilized.

For gain settings 0.5 to 10, the devices allow single-ended measurements with the negative analog input held at GND. The negative analog input can be connected to GND externally using one of the analog inputs or the internal GND connection of the multiplexer in this case. The devices offer a unipolar, straight binary conversion data coding scheme that can be selected using the CODING bit. This coding scheme is beneficial for single-ended measurements, because the full code range is mapped to the 0V to +VREF / Gain voltage range.

For gain settings 16 to 256 the PGA requires some voltage headroom from GND and AVDD on both the positive and negative analog inputs.

The PGA remains active in idle mode, but turns off in standby and power-down mode.