SBOS965D October   2019  – January 2023 LMH32401

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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: Gain = 2 kΩ
    6. 6.6 Electrical Characteristics: Gain = 20 kΩ
    7. 6.7 Electrical Characteristics: Both Gains
    8. 6.8 Electrical Characteristics: Logic Threshold and Switching Characteristics
    9. 6.9 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Switched Gain Transimpedance Amplifier
      2. 7.3.2 Clamping and Input Protection
      3. 7.3.3 ESD Protection
      4. 7.3.4 Differential Output Stage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Ambient Light Cancellation (ALC) Mode
      2. 7.4.2 Power-Down Mode (Multiplexer Mode)
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RGT|16
  • Y|0
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.4.1 Ambient Light Cancellation (ALC) Mode

The LMH32401 device has an integrated DC cancellation loop that cancels and voltage offsets from incidental ambient light. The ALC mode only works when the PD is sinking the photocurrent. The DC cancellation loop is enabled by setting IDC_EN low. Incident ambient light on a photodiode produces a DC current resulting in an offset voltage at the output of the LMH32401's TIA stage. The Functional Block Diagram shows how the ALC loop senses the low-frequency DC offset at the output of the TIA stage and compares it against an internal reference voltage (VREF). The ALC loop then outputs an opposing DC current (IDC) to compensate for the differential offset voltage at its input. The loop has a high-pass cutoff frequency of 100 kHz. The ambient light cancellation loop is disabled when the amplifier is placed in power-down mode.

The shot noise current introduced by the DC cancellation loop increases the overall amplifier noise; so, if the ambient light level is negligible, then disable the loop to improve SNR. The cancellation loop helps save PCB space and system costs by eliminating the need for external AC coupling passive components. Additionally, the extra trace inductance and PCB capacitance introduced by using external AC coupling components degrades the LMH32401 device dynamic performance.