2 W, Filterless, Class-D

Stereo Audio Amplifier

SSM2306

Rev. 0

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FEATURES

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

Ultralow idle current with load resistance

>87% efficiency at 5.0 V, 1.4 W into 8 Ω speaker

Better than 96 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

20 nA ultralow shutdown current

Short-circuit and thermal protection

Pop-and-click suppression

Built-in resistors reduce board component count

Default fixed 18 dB gain and user-adjustable

APPLICATIONS

Mobile phones

MP3 players

Portable gaming

Portable electronics

Educational toys

Notebook computers

GENERAL DESCRIPTION

The SSM2306 is a fully integrated, high efficiency, Class-D stereo

audio amplifier designed to maximize performance for portable

applications. The application circuit requires minimum 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 SSM2306 features ultralow idle current, high efficiency, and

a low noise modulation scheme. It operates with >87% 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 96 dB. PDM modulation offers lower

EMI radiated emissions compared to other Class-D architectures.

The SSM2306 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 to minimize voltage glitches at the output

during turn-on and turn-off, thereby reducing audible noise on

activation and deactivation. The fully differential input of the

SSM2306 provides excellent rejection of common-mode noise

on the input. Input coupling capacitors can be omitted if the dc

The SSM2306 also has excellent rejection of power supply noise,

including noise caused by GSM transmission bursts and RF

rectification.

The SSM2306 has a preset gain of 18 dB that can be reduced by

using external resistors.

The SSM2306 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).

FUNCTIONAL BLOCK DIAGRAM

FET

DRIVER

MODULATOR

0.1µF

VDD

VDD

INTERNAL

OSCILLATOR

OUTR+

OUTR–

OUTL+

OUTL–

BIAS

FET

DRIVER

MODULATOR

INR+

VBATT

2.5V TO 5.0V

INR–

SHUTDOWN

INL+

INL–

GND

GND

10µF

344kΩ

344kΩ

43kΩ

43kΩ

43kΩ

43kΩ

344kΩ

344kΩ

SD

LEFT IN+

LEFT IN–

RIGHT IN–

RIGHT IN+

SSM2306

Figure 1.