SNAS491C February   2010  – January 2025 LM48580

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: VDD = 3.6 V #GUID-238D0643-98EF-4676-B2E1-A584A5DF74F7/SNAS491599
    6. 5.6 Typical Performance Characteristics
  7.   Parameter Measurement Information
  8. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Class H Operation
      2. 6.3.2 Properties of Piezoelectric Elements
      3. 6.3.3 Differential Amplifier Explanation
      4. 6.3.4 Thermal Shutdown
      5. 6.3.5 Gain Setting
    4. 6.4 Device Functional Modes
      1. 6.4.1 Shutdown Function
  9. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
        1. 7.2.1.1 Proper Selection of External Components
          1. 7.2.1.1.1 Boost Converter Capacitor Selection
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Boost Converter Output Capacitor Selection
          1. 7.2.2.1.1 Inductor Selection
          2. 7.2.2.1.2 Diode Selection
        2. 7.2.2.2 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  10. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Community Resources
    4. 8.4 Trademarks
  11. 9 Revision History
  12. 10Mechanical, Packaging, and Orderable Information

6.3.2 Properties of Piezoelectric Elements

Piezoelectric elements such as ceramic speakers or piezoelectric haptic actuators are capacitive in nature. Due to their capacitive nature, piezoelectric elements appear as low impedance loads at high frequencies (typically above 5 kHz). A resistor in series with the piezoelectric element is required to ensure the amplifier does not see a short at high frequencies.

The value of the series resistor depends on the capacitance of the element, the frequency content of the output signal, and the desired frequency response. Higher valued resistors minimize power dissipation at high frequencies, but also impacts the frequency response. This configuration is suited for use with haptic actuators, where the majority of the signal content is typically below 2 kHz. Conversely, lower valued resistors maximize frequency response, while increasing power dissipation at high frequency. This configuration is ideal for ceramic speaker applications, where high frequency audio content needs to be reproduced. Resistor values are typically between 10 Ω and 20 Ω.