Part Numbers with "Z" indicate RoHS Compliance. Boards checked are needed to evaluate this circuit
- EVAL-ADAU1701MINIZ ($195.00) ADAU1701 evaluation board used to evaluate this circuit.
Features & Benefits
- Audio codec with class D amplifier
- Capable of stereo audio processing
- Configurations for both line output and amplified output
Circuit Function & Benefits
This circuit uses one of the ADAU1701 multipurpose (MP) pins to control the active-low shutdown pin of the SSM2306. This connection, with a 10 kΩ pull-up resistor, enables the SigmaDSP program to cleanly disable the Class-D amplifier without pops and clicks.
The Class-D amplifier outputs of the SSM2306 are stable with just a ferrite bead and a 1.0 nF capacitor on each pin before the speaker.
The SSM2306 can take its supply voltage directly from the 5 V supply, such as from a battery, but the ADAU1701 requires a regulated 3.3 V supply, which is generated by the ADP3336. The output voltage of the ADP3336 is programmed to 3.3 V with 140 kΩ and 78.7 kΩ feedback resistors. The output of the regulator is stable with a single capacitor as low as 1.0 μF between the output pins and ground. The 1.0 μF capacitor on the input of the regulator is used for decoupling any stray inductance between the board and the 5 V source. In this circuit, the shutdown pin of the regulator is simply tied to the input voltage so that the IC is enabled when the input voltage is present.
The SSM2301, SSM2302, and SSM2304 Class-D amplifiers differ slightly from the SSM2306 used in this design. These three amplifiers do not require external resistors on the audio inputs to set the gain. The SSM2301 is a mono, rather than a stereo, amplifier.
|SSM2306||2 W, Filterless, Class-D Stereo Audio Amplifier||
|ADAU1701||SigmaDSP® 28/56-Bit Audio Processor with Two ADCs and Four DACs||
|ADP3336||Small, Adjustable Output, 500 mA anyCAP® Low Dropout Regulator||