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

10.1.5 Analog Input Filtering

Analog input filtering serves two purposes:

  1. Limits the effect of aliasing during the sampling process
  2. Reduces external noise from being a part of the measurement

Aliasing occurs when frequency components are present in the input signal that are higher than half the sampling frequency of the ADC (also known as the Nyquist frequency). These frequency components fold back and show up in the actual frequency band of interest below half the sampling frequency. The filter response of the digital filter, as shown in Figure 10-3, repeats at multiples of the sampling frequency, also known as the modulator frequency (fMOD). Signals or noise up to a frequency where the filter response repeats are attenuated to a certain amount by the digital filter depending on the filter architecture. Any frequency components present in the input signal around the modulator frequency, or multiples thereof, are not attenuated and alias back into the band of interest, unless attenuated by an external analog filter.

ADS1114L ADS1115L Effect of AliasingFigure 10-3 Effect of Aliasing

Many sensor signals are inherently band-limited (for example, the output of a thermocouple has a limited rate of change). In this case, the sensor signal does not alias back into the pass band when using a ΔΣ ADC. However, any noise pick-up along the sensor wiring or the application circuitry can potentially alias into the pass band. Power line-cycle frequency and harmonics are one common noise source. External noise can also be generated from electromagnetic interference (EMI) or radio frequency interference (RFI) sources, such as nearby motors and cellular phones. Another noise source typically exists on the printed circuit board (PCB) in the form of clocks and other digital signals. Analog input filtering helps remove unwanted signals from affecting the measurement result.

A first-order resistor-capacitor (RC) filter is (in most cases) sufficient to either totally eliminate aliasing, or to reduce the effect of aliasing to a level within the noise floor of the sensor. Generally, any signal beyond fMOD / 2 is attenuated to a level below the noise floor of the ADC. The digital filter of the ADS111xL attenuates signals to a certain degree. In addition, noise components are usually smaller in magnitude than the actual sensor signal. Therefore, using a first-order RC filter with a cutoff frequency set at the output data rate or 10 times higher is generally a good starting point for a system design.