SBAS444D May   2009  – January 2018 ADS1113 , ADS1114 , ADS1115

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Block Diagrams
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements: I2C
    7. 7.7 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Noise Performance
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagrams
    3. 9.3 Feature Description
      1. 9.3.1 Multiplexer
      2. 9.3.2 Analog Inputs
      3. 9.3.3 Full-Scale Range (FSR) and LSB Size
      4. 9.3.4 Voltage Reference
      5. 9.3.5 Oscillator
      6. 9.3.6 Output Data Rate and Conversion Time
      7. 9.3.7 Digital Comparator (ADS1114 and ADS1115 Only)
      8. 9.3.8 Conversion Ready Pin (ADS1114 and ADS1115 Only)
      9. 9.3.9 SMbus Alert Response
    4. 9.4 Device Functional Modes
      1. 9.4.1 Reset and Power-Up
      2. 9.4.2 Operating Modes
        1. 9.4.2.1 Single-Shot Mode
        2. 9.4.2.2 Continuous-Conversion Mode
      3. 9.4.3 Duty Cycling For Low Power
    5. 9.5 Programming
      1. 9.5.1 I2C Interface
        1. 9.5.1.1 I2C Address Selection
        2. 9.5.1.2 I2C General Call
        3. 9.5.1.3 I2C Speed Modes
      2. 9.5.2 Slave Mode Operations
        1. 9.5.2.1 Receive Mode
        2. 9.5.2.2 Transmit Mode
      3. 9.5.3 Writing To and Reading From the Registers
      4. 9.5.4 Data Format
    6. 9.6 Register Map
      1. 9.6.1 Address Pointer Register (address = N/A) [reset = N/A]
        1. Table 6. Address Pointer Register Field Descriptions
      2. 9.6.2 Conversion Register (P[1:0] = 0h) [reset = 0000h]
        1. Table 7. Conversion Register Field Descriptions
      3. 9.6.3 Config Register (P[1:0] = 1h) [reset = 8583h]
        1. Table 8. Config Register Field Descriptions
      4. 9.6.4 Lo_thresh (P[1:0] = 2h) [reset = 8000h] and Hi_thresh (P[1:0] = 3h) [reset = 7FFFh] Registers
        1. Table 9. Lo_thresh and Hi_thresh Register Field Descriptions
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Basic Connections
      2. 10.1.2 Single-Ended Inputs
      3. 10.1.3 Input Protection
      4. 10.1.4 Unused Inputs and Outputs
      5. 10.1.5 Analog Input Filtering
      6. 10.1.6 Connecting Multiple Devices
      7. 10.1.7 Quickstart Guide
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Shunt Resistor Considerations
        2. 10.2.2.2 Operational Amplifier Considerations
        3. 10.2.2.3 ADC Input Common-Mode Considerations
        4. 10.2.2.4 Resistor (R1, R2, R3, R4) Considerations
        5. 10.2.2.5 Noise and Input Impedance Considerations
        6. 10.2.2.6 First-order RC Filter Considerations
        7. 10.2.2.7 Circuit Implementation
        8. 10.2.2.8 Results Summary
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
    1. 11.1 Power-Supply Sequencing
    2. 11.2 Power-Supply Decoupling
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Related Links
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

10.2.2.7 Circuit Implementation

Table 11 shows the chosen values for this design.

Table 11. Parameters

PARAMETER VALUE
VCM 2.5 V
FSR of ADC ±0.256 V
Output Data Rate 250 SPS
R1, R3 1 kΩ(1)
R2, R4 5 kΩ(1)
R5, R6 100 Ω(1)
CDIFF 0.22 µF
CCM1, CCM2 0.022 µF
(1) 1% precision resistors used

Using Equation 7, if VSHUNT ranges from –50 mV to +50 mV, the application circuit produces a differential voltage ranging from –0.250 V to +0.250 V across the ADC inputs . The ADC is therefore configured at a FSR of ±0.256 V to maximize the dynamic range of the ADC.

The –3 dB cutoff frequencies of the differential low-pass filter and the common-mode low-pass filters are set at 3.6 kHz and 0.36 kHz, respectively.

RSHUNT typically ranges from 0.01 mΩ to 100 mΩ. Therefore, if R1 = R3 = 1 kΩ, a good trade-off exists between the circuit input impedance and input referred resistor noise as explained in the Noise and Input Impedance Considerations section.

A simple resistor divider followed by a buffer amplifier is used to generate VCM of 2.5 V from a 5-V supply.