Silicon Labs looks to simplify Class D audio development

Silicon Laboratories has introduced a USB-based evaluation kit that enables developers to add digital Class D audio capabilities to 32-bit embedded designs based on Silicon Labs’ SiM3U1xx Precision32 microcontrollers (MCUs). The Class D ToolStick kit makes it easy and economical to upgrade basic “buzzer/beeper” alert sounds used in personal medical devices, fitness equipment, high-end toys, small appliances and other consumer electronics products to more sophisticated voice prompts, music, sound clips and even streaming audio.

The SiM3U1xx MCUs are suited for digital Class D power amplification applications without the expense of adding discrete Class D amplifiers. They include a 300 mA high-drive I/O capable of directly driving a small speaker, a crystal-less USB transceiver compatible with the USB audio interface, two 250 ksps 12-bit analogue-to-digital converters (ADCs), and an I2S receiver that supports audio streaming from a PC, a portable music player or a wide range of I2S-enabled audio devices. The only external components required to drive Class D audio are inexpensive inductors, some capacitors and ferrite beads.

In addition to supporting Class D audio capabilities, the new ToolStick also enables developers to add capacitive touch buttons and sliders to their 32-bit embedded systems or use the SiM3U1xx MCU’s high-drive I/Os with pulse-width modulation (PWM) to directly drive other components such as small motors, eliminating the need for separate power field-effect transistors (FETs).

The Class D ToolStick board is powered from USB using the SiM3U1xx’s internal 5 V regulator, and it can play music from a stereo jack, a computer or a recorded message using a simple speaker. The Class D ToolStick provides four modes of operation: sampling data from a portable music player using the MCU’s on-chip ADCs, USB audio streaming from a PC, playing pre-recorded sound clips stored from on-chip flash memory using a common audio compression algorithm, and a voice recorder that stores data in flash using an audio compression algorithm. Developers can easily handle mode transition through capacitive touch buttons and control volume with a capacitive touch slider.

The Class D ToolStick evaluation kit comes complete with hardware Gerber files and software to streamline the process of adding Class D audio to embedded applications. In addition, the ToolStick can serve as a cost-effective, general-purpose development platform for Precision32 MCUs. It features a built-in USB-based debugger/programming interface and accessible pins for easy prototyping. The Class D ToolStick debug interface is fully operational with Silicon Labs’ complimentary Precision32 IDE, compiler and AppBuilder crossbar configuration software, as well as Keil tool chains.


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