Notes: PCM1808 requires external mux for ≥ 2 inputs
The core subsystems include:
Portable Audio Converters with miniDSP
The miniDSP can support:
- Branded third-party algorithms. SRS WOW-HD is a standard feature for all miniDSP devices with stereo DAC. • Due to resource limitations, complex compression algorithms such as AAC and MP3 are not supported.
- Multiband DRC and speaker-protection algorithms to boost loudness and sound quality without damaging the speaker.
How to Use the miniDSP
Each miniDSP device can be programmed via a graphical-development-environment software called PurePath™ Studio. The software is loaded on a host PC and used to configure the codec and miniDSP and to create process flows. Predefined components are provided with a simple “drag/ drop” implementation of advanced audio processing flows. The miniDSP instruction memory is loaded with the customized desired algorithms over an I2C or SPI.
Medium- and High-Power, Analog-Input Class-D Speaker Amplifiers
Output Power per Channel
- Maximum power is decided primarily by power supply (output voltage and current) and speaker impedance.
- Efficiency of Class-D amplifiers is typically between 80% and 90%, which reduces demands on the power supply design.
- The maximum input signal level dictates the required power amplifier gain to achieve the desired output power.
- For best noise performance, the gain should be as low as possible.
Output Filter Design
- Most of TI’s Class-D amplifiers operate without a filter when speaker wires are less than 10 cm.
- When speaker wires are long, place a second-order low-pass (LC) filter as close as possible to the amplifier’s output pins.
- The filter must be designed specifically for the speaker impedance because the load resistance affects the filter’s quality factor, or Q.
- A ferrite bead may also eliminate very high-frequency interference.