SSM2517:  Digital PDM-Input Mono 2.5W Class-D Audio Amplifier

The SSM2517 is a PDM digital input Class-D power amplifier. It provides a solution that offers higher performance than existing DAC plus Class-D solutions. It is ideal for power sensitive applications where system noise can corrupt the small analog signal sent to the amplifier, such as mobile phones and portable media players. The DAC plus analog Sigma Delta architecture enables extremely low real world power consumption from digital audio sources with excellent audio performance. Using the SSM2517, audio can be transmitted digitally to the audio amplifier therebysignificantly reducing the effect of noise sources such as GSM interference or other digital signals on the transmitted audio. It is capable of delivering 2.5 W of continuous output power with <1% THD + N driving a 4 Ω load from a 5.0 V supply.

The SSM2517 features a high efficiency, low noise modulation scheme that requires no external LC output filters. The closedloop, 3-level modulator design retains the benefits of an alldigital 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 96 dB PDM input. Spread-spectrum pulse density modulation is used to provide lower EMI-radiated emissions compared with other Class-D architectures. The SSM2517 has a 5-state gain and sample frequency selection pin that can select two different gain settings, optimized for 3.6V and 5V operation. This same pin also controls the internally digital filtering and clocking that can be set for 64fs or 128fs input sample rates, supporting both 3MHz and 6MHz PDM clock rates.

The SSM2517 has a micropower shutdown mode with a typical shutdown current of 1uA for both power supplies. Shutdown is enabled automatically by gating input clock and data signals. A standby mode can be entered by applying a designated PDM stop condition sequence. The device also includes pop-andclick suppression circuitry. This suppression circuitry minimizes voltage glitches at the output during turn-on and turn-off, reducing audible noise on activation and deactivation. The SSM2517 is specified over the industrial temperature range of −40°C to +85°C. It has built-in thermal shutdown and output short-circuit protection. It is available in a 9-ball, 1.5 mm × 1.5 mm wafer level chip scale package (WLCSP).

Applications

• Mobile Handsets