SBASAV5 December   2023 ADS1114L , ADS1115L

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 I2C Timing Requirements
    7. 6.7 Timing Diagram
    8. 6.8 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 Diagrams
    3. 8.3 Feature Description
      1. 8.3.1 Multiplexer
      2. 8.3.2 Analog Inputs
      3. 8.3.3 Full-Scale Range (FSR) and LSB Size
      4. 8.3.4 Voltage Reference
      5. 8.3.5 Oscillator
      6. 8.3.6 Output Data Rate and Conversion Time
      7. 8.3.7 Digital Comparator
      8. 8.3.8 Conversion-Ready Pin
      9. 8.3.9 SMBus Alert Response
    4. 8.4 Device Functional Modes
      1. 8.4.1 Reset and Power-Up
      2. 8.4.2 Operating Modes
        1. 8.4.2.1 Single-Shot Mode
        2. 8.4.2.2 Continuous-Conversion Mode
    5. 8.5 Programming
      1. 8.5.1 I2C Interface
        1. 8.5.1.1 I2C Address Selection
        2. 8.5.1.2 I2C Interface Speed
          1. 8.5.1.2.1 Serial Clock (SCL) and Serial Data (SDA)
        3. 8.5.1.3 I2C Data Transfer Protocol
        4. 8.5.1.4 Timeout
        5. 8.5.1.5 I2C General-Call (Software Reset)
      2. 8.5.2 Reading and Writing Register Data
        1. 8.5.2.1 Reading Conversion Data or the Configuration Register
        2. 8.5.2.2 Writing the Configuration Register
      3. 8.5.3 Data Format
  10. 9 Register Map
  11. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Basic Connections
      2. 10.1.2 Unused Inputs and Outputs
      3. 10.1.3 Single-Ended Inputs
      4. 10.1.4 Input Protection
      5. 10.1.5 Analog Input Filtering
      6. 10.1.6 Connecting Multiple Devices
      7. 10.1.7 Duty Cycling For Low Power
      8. 10.1.8 I2C Communication Sequence Example
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curve
    3. 10.3 Power Supply Recommendations
      1. 10.3.1 Power-Supply Sequencing
      2. 10.3.2 Power-Supply Decoupling
    4. 10.4 Layout
      1. 10.4.1 Layout Guidelines
      2. 10.4.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.3.2 Analog Inputs

The ADS111xL use a switched-capacitor input stage where capacitors are continuously charged and then discharged to measure the voltage between AINP and AINN. The frequency at which the input signal is sampled is called the sampling frequency or the modulator frequency (fMOD). The ADS111xL has a 1-MHz internal oscillator that is further divided by a factor of 4 to generate fMOD at 250 kHz. The capacitors used in this input stage are small, and to external circuitry, the average loading appears resistive. Figure 8-4 shows this structure. The capacitor values set the resistance and switching rate. Figure 8-5 shows the timing for the switches in Figure 8-4. During the sampling phase, switches S1 are closed. This event charges CA1 to V(AINP), CA2 to V(AINN), and CB to (V(AINP) – V(AINN)). During the discharge phase, S1 is first opened and then S2 is closed. Both CA1 and CA2 then discharge to approximately 0.7 V and CB discharges to 0 V. This charging draws a very small transient current from the source driving the ADS111xL analog inputs. The average value of this current can be used to calculate the effective impedance (Zeff), where Zeff = VIN / IAVERAGE.

ADS1114L ADS1115L Simplified Analog Input CircuitFigure 8-4 Simplified Analog Input Circuit
ADS1114L ADS1115L S1 and S2 Switch TimingFigure 8-5 S1 and S2 Switch Timing

The common-mode input impedance is measured by applying a common-mode signal to the shorted AINP and AINN inputs and measuring the average current consumed by each pin. The common-mode input impedance changes depending on the full-scale range, but is approximately 6 MΩ for the default full-scale range. In Figure 8-4, the common-mode input impedance is ZCM.

The differential input impedance is measured by applying a differential signal to AINP and AINN inputs where one input is held at 0.7 V. The current that flows through the pin connected to 0.7 V is the differential current and scales with the full-scale range. In Figure 8-4, the differential input impedance is ZDIFF.

Make sure to consider the typical value of the input impedance. Unless the input source has a low impedance, the ADS111xL input impedance can affect measurement accuracy. For sources with high-output impedance, buffering can be necessary. Active buffers introduce noise, and also introduce offset and gain errors. Consider all of these factors in high-accuracy applications.

The clock oscillator frequency drifts slightly with temperature; therefore, the input impedances also drift. For most applications, this input impedance drift is negligible, and can be ignored.