2 W Filterless Class-D Stereo Audio Amplifier

The SSM2304 is a fully integrated, high efficiency, Class-D stereo audio amplifier. It is designed to maximize performance for portable applications. The application circuit requires a mini-mum of external components and operates from a single 2.5 V to 5.0 V supply. It is capable of delivering 2 W of continuous output power with less than 10% THD + N driving a 4 Ω load from a 5.0 V supply.

The SSM2304 features a high efficiency, low noise modulation scheme. It operates with 85% efficiency at 1.4 W into 8 Ω from a 5.0 V supply and has a signal-to-noise ratio (SNR) that is better than 98 dB. PDM modulation is used to provide lower EMI-radiated emissions compared with other Class-D architectures.

The SSM2304 has a micropower shutdown mode with a typical shutdown current of 20 nA. Shutdown is enabled by applying a logic low to the SD pin.

The architecture of the device allows it to achieve a very low level of pop and click. This minimizes voltage glitches at the output during turn-on and turn-off, thus reducing audible noise on activation and deactivation.

The fully differential input of the SSM2304 provides excellent rejection of common-mode noise on the input. Input coupling capacitors can be omitted if the dc input common-mode voltage is approximately VDD/2.

The SSM2304 also has excellent rejection of power supply noise, including noise caused by GSM transmission bursts and RF rectification.

The SSM2304 has a preset gain of 18 dB, which can be reduced by using external resistors.

The SSM2304 is specified over the commercial temperature range (−40°C to +85°C). It has built-in thermal shutdown and output short-circuit protection. It is available in a 16-lead, 3 mm × 3 mm lead-frame chip scale package (LFCSP).

Applications

* Notebooks and PCs

* Mobile phones

* MP3 players

* Portable gaming

* Portable electronics

* Educational toys

* Filterless Class-D amplifier with built-in output stage

* 2 W into 4 Ω and 1.4 W into 8 Ω at 5.0 V supply with <10% THD

* 85% efficiency at 5.0 V, 1.4 W into 8 Ω speaker

* Better than 98 dB SNR (signal-to-noise ratio)

* Available in 16-lead, 3 mm × 3 mm LFCSP

* Single-supply operation from 2.5 V to 5.0 V