Filterless High Efficiency

Mono 3 W Class-D Audio Amplifier

SSM2311

Rev. 0

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FEATURES

Filterless Class-D amplifier with Σ-Δ modulation

No sync necessary when using multiple Analog Devices, Inc.,

Class-D amplifiers

3 W into 3 Ω load and 1.4 W into 8 Ω load at 5.0 V supply with

less than 10% total harmonic distortion (THD)

90% efficiency at 5.0 V, 1.4 W into 8 Ω speaker

Better than 98 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 18 dB or user-adjustable gain setting

APPLICATIONS

Mobile phones

MP3 players

Portable gaming

Portable electronics

Educational toys

GENERAL DESCRIPTION

The SSM2311 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 less than 1% THD + N driving a 3 Ω load from a 5.0 V supply.

The SSM2311 features a high efficiency, low noise modulation

scheme that does not require any external LC output filters. The

modulation continues to provide high efficiency even at low output

power. It operates with 90% 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 that

is better than 98 dB. Spread-spectrum pulse density modulation

is used to provide lower EMI-radiated emissions compared with

other Class-D architectures.

The SSM2311 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

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 SSM2311 provides excellent

rejection of common-mode noise on the input. Input coupling

capacitors can be omitted if the dc input common-mode voltage

The default gain of SSM2311 is 18 dB, but users can reduce the gain

by using a pair of external resistors (see the Gain section).

The SSM2311 is specified over the industrial temperature range

(−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).

FUNCTIONAL BLOCK DIAGRAM

SHUTDOWN

FET

DRIVER

MODULATOR

0.1µF

VDD

GND

OSCILLATOR

POP-AND-CLICK

SUPPRESSION

OUT+

OUT–

BIAS

IN+

VBATT

2.5V TO 5.0V

IN–

10µF

300kΩ

300kΩ

37.5kΩ

37.5kΩ

SD

AUDIO IN–

AUDIO IN+

SSM2311

GAIN =

300kΩ

Figure 1.