ZHCSMM2C March   2022  – October 2023 LMH34400

PRODUCTION DATA  

  1.   1
  2. 特性
  3. 应用
  4. 说明
  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 支持资源
    5. 8.5 Trademarks
    6. 8.6 静电放电警告
    7. 8.7 术语表
  10. Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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Power-Down Mode (Multiplexer Mode)

The LMH34400 can be placed in low-power mode by setting EN high, which helps in saving system power. Enabling low-power mode puts the outputs of the internal amplifiers in the LMH34400 in a high-impedance state.

Figure 6-1 shows how this device feature can further save board space and cost by eliminating the need for a discrete high-speed multiplexer, if a system consists of several photodiode and amplifier channels multiplexed to single time-of-flight detector circuit. The disabled channel outputs are not an ideal open circuit; therefore, as the number of multiplexed channels increases, the disabled channels begin to load the enabled channel. An additional isolation resistor helps to reduce the impact of reflections from disabled channels. Multiplexing more than four channels in parallel degrades the performance of the enabled channel.

When the amplifier is in low-power mode, the clamp circuitry is still active thereby protecting the TIA input. The ambient light cancellation loop is disabled when the amplifier is placed in power-down mode. When the LMH34400 device is brought out of power-down operation, the ambient light cancellation loop requires several time constants to settle. The time constant is based on the 400-kHz cutoff frequency of the loop.

GUID-20220216-SS0I-02VZ-6J1W-NPZMX51WQNH8-low.svg Figure 6-1 Configuring Two LMH34400 Devices in Multiplexer Mode