SBAS473E May   2009  – January 2018 ADS1013 , ADS1014 , ADS1015

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 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 (ADS1014 and ADS1015 Only)
      8. 8.3.8 Conversion Ready Pin (ADS1014 and ADS1015 Only)
      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
      3. 8.4.3 Duty Cycling For Low Power
    5. 8.5 Programming
      1. 8.5.1 I2C Interface
        1. 8.5.1.1 I2C Address Selection
        2. 8.5.1.2 I2C General Call
        3. 8.5.1.3 I2C Speed Modes
      2. 8.5.2 Slave Mode Operations
        1. 8.5.2.1 Receive Mode
        2. 8.5.2.2 Transmit Mode
      3. 8.5.3 Writing To and Reading From the Registers
      4. 8.5.4 Data Format
    6. 8.6 Register Map
      1. 8.6.1 Address Pointer Register (address = N/A) [reset = N/A]
        1. Table 4. Address Pointer Register Field Descriptions
      2. 8.6.2 Conversion Register (P[1:0] = 0h) [reset = 0000h]
        1. Table 5. Conversion Register Field Descriptions
      3. 8.6.3 Config Register (P[1:0] = 1h) [reset = 8583h]
        1. Table 6. Config Register Field Descriptions
      4. 8.6.4 Lo_thresh (P[1:0] = 2h) [reset = 8000h] and Hi_thresh (P[1:0] = 3h) [reset = 7FFFh] Registers
        1. Table 7. Lo_thresh and Hi_thresh Register Field Descriptions
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Basic Connections
      2. 9.1.2 Single-Ended Inputs
      3. 9.1.3 Input Protection
      4. 9.1.4 Unused Inputs and Outputs
      5. 9.1.5 Analog Input Filtering
      6. 9.1.6 Connecting Multiple Devices
      7. 9.1.7 Quickstart Guide
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Shunt Resistor Considerations
        2. 9.2.2.2 Operational Amplifier Considerations
        3. 9.2.2.3 ADC Input Common-Mode Considerations
        4. 9.2.2.4 Resistor (R1, R2, R3, R4) Considerations
        5. 9.2.2.5 Noise and Input Impedance Considerations
        6. 9.2.2.6 First-order RC Filter Considerations
        7. 9.2.2.7 Circuit Implementation
        8. 9.2.2.8 Results Summary
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Power-Supply Sequencing
    2. 10.2 Power-Supply Decoupling
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Related Links
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.2.2.5 Noise and Input Impedance Considerations

If vn_res represents the input-referred rms noise from all the resistors, vn_op represents the input-referred rms noise of OPA333, and vn_ADC represents the input-referred rms noise of ADS1015, the total input-referred noise of the entire system, vN, can be approximated by Equation 11.

Equation 11. vN2 = vn_res2 + vn_op2 + vn_ADC/ (1 + R2 / R1)2

It is important to note that the ADC noise contribution, vn_ADC, is attenuated by the non-inverting gain stage.

If the gain of the noninverting gain stage is high (≥ 5), a good approximation for vn_res2 is given by Equation 12. The noise contribution from resistors R2, R4, R5, and R6 when referred to the input is smaller in comparison to R1 and R3 and can be neglected for approximation purposes.

Equation 12. vn_res2 = 4 · k · T · (R1 + R3) · Δf

where

  • k = Boltzmann constant
  • T = temperature (in kelvins)
  • Δf = noise bandwidth

An approximation for the input impedance, RIN, of the application circuit is given by Equation 13. RIN can be modeled as a resistor in parallel with the shunt resistor, and can contribute to additional gain error.

Equation 13. RIN = R3 + R4

From Equation 12 and Equation 13, a trade-off exists between vN and RIN. If R3 increases, vn_res increases, and therefore, the total input-referred rms system noise, vN, increases. If R3 decreases, the input impedance, RIN, drops, and causes additional gain error.