Filterless, High Efficiency,

Mono 2.5 W Class-D Audio Amplifier

SSM2377

Rev. 0

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FEATURES

Filterless, Class-D amplifier with spread-spectrum

Σ-Δ modulation

2.5 W into 4 Ω load and 1.4 W into 8 Ω load at 5.0 V supply

with <1% total harmonic distortion plus noise (THD + N)

92% efficiency at 5.0 V, 1.4 W into 8 Ω speaker

>100 dB signal-to-noise ratio (SNR)

High PSRR at 217 Hz: 80 dB

Ultralow EMI emissions

Single-supply operation from 2.5 V to 5.5 V

Gain select function: 6 dB or 12 dB

Fixed input impedance of 80 kΩ

100 nA shutdown current

Short-circuit and thermal protection with autorecovery

Available in a 9-ball, 1.2 mm × 1.2 mm WLCSP

Pop-and-click suppression

APPLICATIONS

Mobile phones

MP3 players

Portable electronics

GENERAL DESCRIPTION

The SSM2377 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 2.5 W of continuous output power

with <1% THD + N driving a 4 Ω load from a 5.0 V supply.

The SSM2377 features a high efficiency, low noise modulation

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

lation operates with high efficiency even at low output power.

The SSM2377 operates with 92% efficiency at 1.4 W into 8 Ω

from a 5.0 V supply and has an SNR of >100 dB.

Spread-spectrum pulse density modulation (PDM) is used to

provide lower EMI-radiated emissions compared with other

Class-D architectures. The inherent randomized nature of

spread-spectrum PDM eliminates the clock intermodulation

(beating effect) of several amplifiers in close proximity.

The SSM2377 produces ultralow EMI emissions that signifi-

cantly reduce the radiated emissions at the Class-D outputs,

particularly above 100 MHz. The SSM2377 passes FCC Class B

radiated emission testing with 50 cm, unshielded speaker cable

without any external filtering. The ultralow EMI emissions of the

SSM2377 are also helpful for antenna and RF sensitivity problems.

The device is configured for either a 6 dB or a 12 dB gain setting

by connecting the GAIN pin to the VDD pin or the GND pin,

respectively. Input impedance is a fixed value of 80 kΩ, indepen-

dent of the gain select operation.

The SSM2377 has a micropower shutdown mode with a typical

shutdown current of 100 nA. Shutdown is enabled by applying

a logic low to the SD pin.

The device also includes pop-and-click suppression circuitry,

which minimizes voltage glitches at the output during turn-on

and turn-off, reducing audible noise on activation and deactivation.

Built-in input low-pass filtering is also included to suppress out-

of-band noise interference to the PDM modulator.

The SSM2377 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 halide-free, 9-ball, 0.4 mm

pitch, 1.2 mm × 1.2 mm wafer level chip scale package (WLCSP).

FUNCTIONAL BLOCK DIAGRAM

FET

DRIVER

MODULATOR

(Σ-Δ)

0.1µF

VDD

OUT+

OUT–

BIAS

IN+

80kΩ

80kΩ

POWER SUPPLY

2.5V TO 5.5V

IN–

INTERNAL

OSCILLATOR

POP/CLICK

AND EMI

SUPPRESSION

GND

10µF

22nF

22nF

SHUTDOWN

SD

GAIN SELECT

AUDIO IN+

AUDIO IN–

SSM2377

GAIN

GAIN = 6dB OR 12dB

Figure 1.