SBOSA28B August   2023  – August 2026 LOG200

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 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 High Speed, Logarithmic Current-to-Voltage Conversion
      2. 6.3.2 Voltage and Current References
      3. 6.3.3 Adaptive Photodiode Bias
      4. 6.3.4 Auxiliary Operational Amplifier
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Logarithmic Transfer Function
        1. 7.1.1.1 Logarithmic Conformity Error
        2. 7.1.1.2 Error Analysis Example
    2. 7.2 Typical Application
      1. 7.2.1 Optical Current Sensing
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

7.2.1.2 Detailed Design Procedure

The G8195-12 photodiode was used with a fixed reverse bias voltage of 5V. The cathode was connected to the VS+ 5V supply, and the anode to the I1 pin. GND is used for the VCM potential. The IBIAS feature and REF165 voltage reference were not needed; therefore, the IBIAS and REF165 pins are left floating. The auxiliary amplifier was not needed; therefore, the auxiliary amplifier was placed in a buffer configuration and used to buffer the REF25 reference voltage.

GND was used for the REFA input of the logarithmic difference amplifier. The circuit output follows the expression

Equation 21. V L O G O U T = 250mV × log 10 I 1 1µA

such that the expected output for a 100nA input is –500mV, the expected output for a 10µA input is 250mV, and so on.