SBOSA63A December   2020  – November 2021 LMH32404-Q1

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
    6. 6.6 Electrical Characteristics: Logic Threshold and Switching Characteristics
    7. 6.7 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 Clamping and Input Protection
      2. 7.3.2 ESD Protection
      3. 7.3.3 Differential Output Stage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Ambient Light Cancellation (ALC) Mode
      2. 7.4.2 Channel Multiplexer Mode
      3. 7.4.3 Low-Power Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Standard TIA Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Increase Channel Density for Optical Front-End Systems
        1. 8.2.2.1 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

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

7.4.3 Low-Power Mode

The LMH32404-Q1 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 LMH32404-Q1, including the differential outputs, in a high-impedance state.

If a system consists of high number of amplifier channels multiplexed to a few ADC channels. Figure 7-4 shows how this device feature can further save board space and cost by eliminating the need for a discrete high-speed multiplexer. The disabled LMH32404-Q1 outputs are high-impedance so multiple LMH32404-Q1 device outputs can be directly shorted to each other. If one LMH32404-Q1 device is enabled and others are disabled, the disabled devices will not load the enabled device. This further makes the LMH32404-Q1 easy to use in photodiode array applications.

When the amplifier is in its 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 low-power mode. When the LMH32404-Q1 is brought out of low-power 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.

Figure 7-4 Configuring Three LMH32404-Q1 Devices to Drive Four ADC Channels