The SSM4567 is a digital input Class-D power amplifier that includes an integrated boost converter, allowing higher output power than with a normal battery supply. This means that maximum output power is constant across the battery voltage range. The SSM4567 is ideal for power sensitive applications where system noise can corrupt the small analog signal sent to the amplifier, such as mobile phones, tablets, and portable media players.

The SSM4567 combines an audio digital-to-analog converter (DAC), a power amplifier, and PDM or PCM (I2S/TDM) digital audio interfaces on a single chip. Using the SSM4567, audio can be transmitted digitally to the audio amplifier, significantly reducing the effect of noise sources on the transmitted audio and eliminate the need for input coupling capacitors. The SSM4567 is capable of delivering 2.5 W of continuous output power with <1% THD + N driving a 4ohms load from a 3.6V supply. The SSM4567 can be controlled by I2C, PDM pattern control, or TDM control. It can also operate in standalone mode without a control interface.

The SSM4567 includes circuitry to sense output current, output voltage, and the VBAT supply voltage. Current sensing is performed using an on-chip sense resistor that is connected between an output pin and the load. Output current and voltage are sent to an ADC. The outputs of these ADCs are available on the digital serial output port. The VBAT supply voltage can be used with an automatic gain control circuit that is fully configurable. This AGC can limit the maximum output at low battery voltages to avoid drawing too much current from the battery, thereby extending battery life. The SSM4567 features a high efficiency, low noise modulation scheme that requires no external LC output filters. The closed-loop, five-level modulator design retains the benefits of an all digital amplifier, yet enables very good PSRR and audio performance. The modulation continues to provide high efficiency even at low output power and has an SNR of 104 dB, A-weighted. Spread spectrum pulse density modulation is used to provide lower EMI radiated emissions compared with other Class-D architectures.