Audio Subsystem with Class-D Speaker

and Capless Headphone Driver

SSM2804

Rev. 0

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FEATURES

3 single-ended stereo audio inputs with optional

differential mode

Stereo, 1.4 W, filterless Class-D amplifiers with Σ-Δ modulation

Integrated receiver path bypass switch

Configurable, high performance capless headphone output

with true ground Class-G technology

Optional hardware-based headphone level limiter

Volume control

Flexible input/output mixing

Output mode control

EMI emissions control

Automatic level control (ALC)

Adjustable headphone level limiter

Low shutdown current

Short-circuit and thermal protection

Pop-and-click suppression

Available in a 30-ball, 2.5 mm × 3.0 mm WLCSP

APPLICATIONS

Mobile phones

Portable multimedia devices

GENERAL DESCRIPTION

The SSM2804 is an audio subsystem designed specifically for

mobile phones and portable multimedia devices. This highly

flexible subsystem includes three input channels that can be

configured as single-ended stereo or monaural differential for

multimedia audio sources.

Each set of inputs is independently adjustable with the 2-wire

in steps of 1 dB. Each set of input channels also offers the choice

of variable input impedance PGA mode or fixed input impedance

boost mode. The input signals are then mixed and routed to the

desired set of outputs. This configuration is set using the 2-wire

The SSM2804 includes three selectable output modes.

The first output mode is a stereo Class-D speaker driver capable

of delivering 2 × 1.4 W of continuous power to an 8 Ω bridge-tied

load (BTL) with 1% THD + N when using a 5 V supply. This

Class-D amplifier incorporates three-level Σ-Δ output modulation

designed to increase battery life and improve EMI performance.

with a gain range from +12 dB to −63 dB in 31 steps.

The second output mode is a pair of high performance head-

phone drivers capable of delivering 20 mW per channel into

stereo 32 Ω single-ended loads with 1% THD + N. The stereo

headphone drivers use a highly efficient, true ground centered

Class-G architecture. The headphone outputs incorporate

to −75 dB in 32 steps.

The third output mode is an integrated receiver path bypass

switch for passing voice signals from the audio baseband.

The SSM2804 is specified over the industrial temperature range

of −40°C to +85°C. It has built-in thermal shutdown and output

short-circuit protection. The SSM2804 is available in a 30-ball,

2.5 mm × 3.0 mm wafer level chip scale package (WLCSP).