Filterless, High Efficiency,

Mono 3 W Class-D Audio Amplifier

SSM2335

Rev. 0

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FEATURES

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

>96 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 SSM2335 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 SSM2335 features a high efficiency, low noise modulation

scheme that requires no external LC output filters. The modu-

lation 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 >96 dB. Spread-spectrum pulse density modulation is used

to provide lower EMI-radiated emissions compared with other

Class-D architectures.

The SSM2335 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 SSM2335 provides excellent

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

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

The default gain of the SSM2335 is 18 dB, but users can reduce the

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

The SSM2335 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).

FUNCTIONAL BLOCK DIAGRAM

SHUTDOWN

0.1µF

VDD

POP-AND-CLICK

SUPPRESSION

OUT–

OUT+

IN+

VBATT

2.5V TO 5.5V

IN–

MODULATOR

(Σ-Δ)

GND

10µF

47nF*

*INPUT CAPACITORS ARE OPTIONAL IF INPUT DC COMMON-MODE

47nF*

SD

AUDIO IN–

AUDIO IN+

SSM2335

20kΩ

160kΩ

160kΩ

FET

DRIVER

20kΩ

INTERNAL

OSCILLATOR

BIAS

Figure 1.