SBOSA56C March   2022  – October 2023 LMH34400

PRODUCTION DATA  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Pin Configuration and Functions
  6. 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 Electrical Characteristics: Logic Threshold and Switching Characteristics
    7. 5.7 Typical Characteristics
  7. Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Clamping and Input Protection
      2. 6.3.2 ESD Protection
      3. 6.3.3 Single-Ended Output Stage
    4. 6.4 Device Functional Modes
      1. 6.4.1 Ambient Light Cancellation Mode
      2. 6.4.2 Power-Down Mode (Multiplexer Mode)
  8. Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 LMH34400 Test Circuit
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curves
      2. 7.2.2 LMH34400 Signal Chain With Comparator
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 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. Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
    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. Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • DRL|6
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Clamping and Input Protection

The LMH34400 is designed to work with photodiode (PD) configurations that can source or sink current; the LMH34400, however, is optimized for a sinking current configuration. It is assumed that the LMH34400 device is being used with a PD that is configured with its cathode tied to the amplifier input and the anode tied to a negative supply voltage, unless stated otherwise.

The LMH34400 features two internal clamps, a fast recovery clamp and a soft clamp. The fast recovery clamp is the active clamp when the photodiode is sinking a photocurrent. The soft clamp is the active clamp when the photodiode is sourcing a photocurrent.

Stray reflections from nearby objects with high reflectivity can produce large output current pulses from the PD. The linear input range of the LMH34400 is approximately 30 µA. Input currents in excess of the linear current range cause the internal nodes of the amplifier to saturate, which increases the amplifier recovery time. The end result is a broadening of the output pulse leading to blind zones in the system. To protect against this condition, the LMH34400 features an integrated clamp that absorbs and diverts the excess current to the positive supply (VDD) when the amplifier detects its nodes entering a saturated condition. The integrated clamp minimizes the pulse extension to less than a few nanoseconds for input pulses up to 100 mA. When the amplifier is in low-power mode, the clamp circuitry is still active, thereby protecting the TIA input.