Filterless, High Efficiency, Mono 3 W Class-D Audio Amplifier

The SSM2315 is a fully integrated, high efficiency, Class-D audio amplifier. It is designed to maximize performance for mobile phone applications. The application circuit requires a minimum of external components and operates from a single 2.5 V to 5.5 V supply. It is capable of delivering 3 W of continuous output power with <1% THD + N driving a 3 Ω load from a 5.0 V supply.

The SSM2315 features a high efficiency, low noise modulation scheme that requires no external LC output filters. The modulation continues to provide high efficiency even at low output power. It operates with 93% efficiency at 1.4 W into 8 Ω or 85% efficiency at 3 W into 3 Ω from a 5.0 V supply and has an SNR of >103 dB. Spread-spectrum pulse density modulation is used to provide lower EMI-radiated emissions compared with other Class-D architectures.

The SSM2315 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 device also includes pop-and-click 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 fully differential input of the SSM2315 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 default gain of the SSM2315 is 6 dB, but users can reduce the gain by using a pair of external resistors.

The SSM2315 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 phones

* MP3 players

* Portable gaming

* Portable electronics

* Educational toys

* Filterless Class-D amplifier with Σ-Δ modulation

* No sync necessary when using multiple Class-D amplifiers from Analog Devices, Inc.

* 3 W into 3 Ω load and 1.4 W into 8 Ω load at 5.0 V supply with <1% total harmonic distortion (THD + N)

* 93% efficiency at 5.0 V, 1.4 W into 8 Ω speaker

* >103 dB signal-to-noise ratio (SNR)

* Single-supply operation from 2.5 V to 5.5 V

* 20 nA ultralow shutdown current

* Short-circuit and thermal protection

* Available in 9-ball, 1.5 mm × 1.5 mm WLCSP

* Pop-and-click suppression

* Built-in resistors reduce board component count

* Default fixed 6 dB or user adjustable gain setting