TIDUFC9 May   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Codec Design
      2. 2.2.2 Class-D Amplifier
        1. 2.2.2.1 Audio Filter Design
      3. 2.2.3 Power Design
      4. 2.2.4 EMC, EMI Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TAC5312-Q1
      2. 2.3.2 TAS5441-Q1
      3. 2.3.3 LMR43620-Q1
      4. 2.3.4 TPS7A52-Q1
      5. 2.3.5 TPD2E007
  9. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 Board Connection
      2. 3.1.2 Configuring the Board
    2. 3.2 Software Requirements
      1. 3.2.1 Firmware for Bench Tests
    3. 3.3 Test Setup
    4. 3.4 Test Results
      1. 3.4.1 Audio Performance
      2. 3.4.2 Power Tests
      3. 3.4.3 EMI, EMC Test Results
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 Bill of Materials
      3. 4.1.3 PCB Layout Recommendations
        1. 4.1.3.1 Layout Prints
      4. 4.1.4 Altium Project
      5. 4.1.5 Gerber Files
      6. 4.1.6 Assembly Drawings
    2. 4.2 Documentation Support
    3. 4.3 Support Resources
    4. 4.4 Trademarks
  11. 5About the Author

2 System Overview

Governing bodies around the world have implemented specific legislation to require automotive companies to install emergency call (eCall) systems to reduce emergency response times and save lives. eCall systems are activated during a collision or emergency situation and automatically facilitate a call to emergency services. The state of a vehicle after a collision is difficult to predict and can include a disconnected battery, trapped passengers, and a noisy environment. For this reason, the eCall module requires an independent battery power source and must be able to sustain hands-free calls for approximately ten minutes depending on specific regional legislation. Therefore, the audio devices selected for this reference design are excellent choices for low power consumption while still enabling a loud and clear conversation with an emergency operator. In addition, both the TAC5312-Q1 codec and TAS5441-Q1 speaker amplifier include integrated diagnostics and protection features that optimize design and reduce the system cost.

Figure 2-1 shows the entire block diagram containing power management, an MCU, a connectivity module, and audio. The MCU receives inputs from the rest of the vehicle and activates the call if an accident occurs. The power management is able to run off of the main battery of a car or a smaller back-up battery integrated into the eCall module. The wireless module makes the call and uses a full duplex digital audio signal to interface with the audio subsystem. The audio subsystem drives the speakers and handles the microphone input.

TIDA-060048 System Integration of eCall Subsystem Figure 2-1 System Integration of eCall Subsystem

The audio subsystem consists of a class-D audio amplifier and an audio codec. The audio codec connects the digital audio input from the connectivity module to the class-D amplifier which drives the speaker. The codec must also convert the microphone inputs to a digital signal to communicate back to the connectivity module.