MCU comes with class D speaker amp to embed audio playback

September 04, 2014 // By Graham Prophet
Lapis Semiconductor has a low power microcontroller that integrates an 8bit low power MCU core, speech synthesis circuit, high efficiency class D speaker amp, non-volatile memory, and oscillator circuit on a single chip, making audio playback possible by connecting to a speaker.

The ML610Q304 also provides hardware-based audio playback operation that minimises the load placed on the MCU for system control processing, and the high-efficiency Class D amp reduces current consumption during audio playback by approximately 40% relative to conventional products while maintaining volume and is easier to incorporate into battery-driven devices.

Hardware-based voice playback function simplifies design; using hardware lightens the load on the MCU for system control processing and simplifies playback considerably. A monolithic design with integrated microcontroller and audio playback function reduces the number of parts required and contributes to device miniaturisation; all functions required for audio playback are incorporated into a single chip, including a low-power MCU, speech synthesis circuit, high efficiency Class D speaker amp, non-volatile memory, and high accuracy oscillator circuit, in a 5 x 5mm, 28pin package (WQFN).

The device has multiple fail-safe functions for reliability; speaker terminal disconnection detection detects a no-playback condition due to disconnection between the microcontroller and speakers by monitoring for changes in resistance value between the speaker terminals, and can alert users by LEDs. Speaker terminal short-circuit detection detects no-playback condition due to short-circuit by monitoring the voltage level of the speaker terminals and shuts down operation in order to prevent possible damage. The class D speaker amp has overcurrent prevention ensuring that the sound generator circuit (PWM circuit) does not stay fixed at the H level for more than a specified amount of time in order to prevent excessive heat generation due to overcurrent. A complete support system is offered, including a reference board (ML610Q304) and software development environment.

The device also has;

  1. High-performance 8bit RISC core;
  2. Integrated high efficiency Class D speaker amp (3.0V: 0.45W, 5.0V: 1.0W);
  3. High-precision oscillator: 8.192 MHz, 32.768 kHz [±1.5% (-10 to 50℃), ±3.0% (-40 to 85℃)];
  4. 96 kB Flash;
  5. 2 kB data Flash;
  6. 1 kB RAM;
  7. 8 bit timer x 4 (two 8bit timers can be used as a 16bit timer);
  8. 3channel 10bit