Filterless High Efficiency

Mono 1.4 W Class-D Audio Amplifier

SSM2301

Rev. A

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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.

1.4 W into 8 Ω at 5.0 V supply with less than 1% THD + N

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

Greater than 98 dB SNR (signal-to-noise ratio)

Single-supply operation from 2.5 V to 5.0 V

20 nA ultralow shutdown current

Short-circuit and thermal protection

Available in 8-lead, 3 mm × 3 mm LFCSP and MSOP packages

Pop-and-click suppression

Built-in resistors reduce board component count

Fixed and user-adjustable gain configurations

APPLICATIONS

Mobile phones

MP3 players

Portable gaming

Portable electronics

Educational toys

GENERAL DESCRIPTION

The SSM2301 is a fully integrated, high efficiency, Class-D audio

amplifier 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 5.0 V

supply. It is capable of delivering 1.4 W of continuous output

power with less than 1% THD + N driving an 8 Ω load from

a 5.0 V supply.

The SSM2301 features a high efficiency, low noise modulation

scheme that does not require external LC output filters. The modu-

lation provides high efficiency even at low output power.

The SSM2301 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 greater than 98 dB. Spread-spectrum modulation is used to

provide lower EMI-radiated emissions compared with other

Class-D architectures.

The SSM2301 has a micropower shutdown mode with a maximum

shutdown current of 30 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 SSM2301 provides excellent

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

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

The SSM2301 also has excellent rejection of power supply noise,

including noise caused by GSM transmission bursts and RF

rectification. PSRR is typically 63 dB at 217 Hz.

The gain can be set to 6 dB or 12 dB by utilizing the gain control

select pin connected respectively to ground or to VDD. Gain

can also be adjusted externally by inserting a resistor in series

with each input pin.

The SSM2301 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 both an 8-lead, 3 mm ×

3 mm lead-frame chip scale package (LFCSP) and an 8-lead

MSOP package.

FUNCTIONAL BLOCK DIAGRAM

SHUTDOWN

GAIN

CONTROL

FET

DRIVER

MODULATOR

0.1µF

VDD

GND

OSCILLATOR

POP/CLICK

SUPPRESSION

OUT+

OUT–

BIAS

IN+

VBATT

2.5V TO 5.0V

IN–

GAIN

10µF

NOTES

SD

AUDIO IN–

AUDIO IN+

SSM2301

Figure 1.