SBASB61 August   2026 ADS114S18 , ADS124S18

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  Power-Scalable Speed Modes
      5. 7.3.5  Clock Source
      6. 7.3.6  Delta-Sigma Modulator
      7. 7.3.7  Digital Filter
        1. 7.3.7.1 Sinc3 and Sinc4 Filters
        2. 7.3.7.2 Sinc4 + Sinc1 Filter
        3. 7.3.7.3 FIR Filter
        4. 7.3.7.4 50Hz and 60Hz Line Cycle Rejection
        5. 7.3.7.5 Digital Filter Latency
        6. 7.3.7.6 Global-Chop Mode
      8. 7.3.8  Excitation Current Sources (IDACs)
      9. 7.3.9  Burn-Out Current Sources (BOCS)
      10. 7.3.10 Bias Voltage Generator (VBIAS)
      11. 7.3.11 General Purpose IOs (GPIOs)
        1. 7.3.11.1 ALERT Output
        2. 7.3.11.2 FAULT Output
      12. 7.3.12 Offset and Gain Calibration Coefficients
      13. 7.3.13 Digital Comparator
      14. 7.3.14 System Monitors
        1. 7.3.14.1 Internal Short (Offset Calibration)
        2. 7.3.14.2 Internal Temperature Sensor
        3. 7.3.14.3 External Reference Voltage Readback
        4. 7.3.14.4 Power-Supply Readback
      15. 7.3.15 Monitors and Status Flags
        1. 7.3.15.1 Reset (RESETn flag)
        2. 7.3.15.2 AVDD Undervoltage Monitor (AVDD_UVn flag)
        3. 7.3.15.3 Reference Undervoltage Monitor (REF_UVn flag)
        4. 7.3.15.4 SPI CRC Fault (SPI_CRC_FAULTn flag)
        5. 7.3.15.5 Register Map CRC Fault (REG_MAP_CRC_FAULTn flag)
        6. 7.3.15.6 Internal Memory Fault (MEM_FAULTn flag)
        7. 7.3.15.7 Register Write Fault (REG_WRITE_FAULTn flag)
        8. 7.3.15.8 Digital Comparator Alert (COMP_ALERTn flag)
    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 Pin
        3. 7.4.1.3 Reset by Register Write
        4. 7.4.1.4 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 Sequencer Mode
          1. 7.4.2.3.1 Configuring the Sequencer
          2. 7.4.2.3.2 Starting and Stopping the Sequencer (START/STOP bits and START pin)
          3. 7.4.2.3.3 Sequencer Status Bits
    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 Register Map CRC
      11. 7.5.11 Conversion Data Format
  9. 8 Register Map
    1. 8.1 Status and General Configuration Page Registers
    2. 8.2 Step Configuration Page Registers
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Serial Interface Connections
      2. 9.1.2 Unused Inputs and Outputs
      3. 9.1.3 Interfacing With Multiple Devices
      4. 9.1.4 Device Initialization and Starting the Sequencer
      5. 9.1.5 Sequencer Configuration Strategy Example
    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
      4. 9.2.4 Autonomous Power Supply Monitoring
        1. 9.2.4.1 Design Requirements
        2. 9.2.4.2 Detailed Design Procedure
    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 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

7.3.9 Burn-Out Current Sources (BOCS)

To help detect potential sensor faults, the ADS1x4S1x provide a pair of programmable burn-out current sources (BOCS). Use the STEPx_BOCS[1:0] bits to enable the current sources and to set the values to 0.2μA, 1μA, or 10μA.

The BOCS connect to the PGA inputs after the internal multiplexer. When enabled, one BOCS sources current from AVDD to the selected positive analog input (AINP) and the other BOCS sinks current from the selected negative analog input (AINN) to AVSS.

In case of an open-circuit in the external sensor or a sensor wire disconnection, these BOCS pull the positive input toward AVDD and the negative input toward AVSS, resulting in a full-scale reading. A full-scale reading can also indicate that the sensor is overloaded or that the reference voltage is absent.

A near-zero reading can indicate a shorted sensor. Distinguishing a shorted sensor condition from a normal reading can be difficult, especially if an RC filter is used at the inputs. The current sources create a voltage drop across the external filter resistors and the residual resistance of the internal multiplexer. That means, even when the sensor is shorted, a small voltage is present at the PGA inputs and the ADC consequently outputs a voltage larger than zero. The residual resistance of the internal multiplexer typically ranges from about 400Ω at AVDD = 3.3V to 1.6kΩ at AVDD = 1.8V.

The ADC readings of a functional sensor can be corrupted when the burn-out current sources are enabled. Therefore, disable the burn-out current sources when performing precision measurements, and only enable the BOCS to test for sensor fault conditions during a dedicated diagnostic measurement.

Disable the BOCS when using global-chop mode (GC_EN = 1b). The burn-out current source function is not compatible with global-chop mode.

The burn-out current sources remain active in idle mode, but turn off in standby and power-down mode.