2 W, Filterless, Class-D
Stereo Audio Amplifier
Data Sheet
SSM2306
Rev. A Document Feedback
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FEATURES
Filterless Class-D amplifier with built-in output stage
2 W into 4 Ω and 1.4 W into 8 Ω at 5.0 V supply
Ultralow idle current with load resistance
>87% efficiency at 5.0 V, 1.4 W into 8 Ω speaker
Better than 96 dB signal-to-noise ratio (SNR)
Available in a 16-lead, 3 mm × 3 mm LFCSP
Single-supply operation from 2.5 V to 5.0 V
20 nA ultralow shutdown current
Short-circuit and thermal protection
Pop-and-click suppression
Built-in resistors reduce board component count
Default fixed 18 dB gain and user-adjustable
APPLICATIONS
Mobile phones
MP3 players
Portable gaming
Portable electronics
Educational toys
Notebook computers
GENERAL DESCRIPTION
The SSM2306 is a fully integrated, high efficiency, Class-D stereo
audio amplifier designed to maximize performance for portable
applications. The application circuit requires minimum external
components and operates from a single 2.5 V to 5.0 V supply. It
is capable of delivering 2 W of continuous output power with less
than 10% total harmonic distortion plus noise (THD + N)
driving a 4 Ω load from a 5.0 V supply.
The SSM2306 features an ultralow idle current, high efficiency,
and a low noise modulation scheme. It operates with >87%
efficiency at 1.4 W into 8 Ω from a 5.0 V supply and has a
signal-to-noise ratio (SNR) that is better than 96 dB. Pulse-
density modulation (PDM) offers lower electromagnetic
interference (EMI) radiated emissions compared to other
Class-D architectures.
The SSM2306 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 architecture of the device allows it to achieve a very low level
of pop and click to minimize voltage glitches at the output during
turn-on and turn-off, thereby reducing audible noise on activation
and deactivation. The fully differential input of the SSM2306
provides excellent rejection of common-mode noise on the input.
Input coupling capacitors can be omitted if the dc input
common-mode voltage is approximately V
DD
/2.
The SSM2306 also has excellent rejection of power supply noise,
including noise caused by GSM transmission bursts and RF
rectification.
The SSM2306 has a preset gain of 18 dB that can be reduced by
using external resistors.
The SSM2306 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 a 16-lead, 3 mm × 3 mm
lead frame chip scale package (LFCSP).
FUNCTIONAL BLOCK DIAGRAM
FET
DRIVER
MODULATOR
0.1µF
VDDVDD
INTERNAL
OSCILLATOR
OUTR+
OUTR–
OUTL+
OUTL–
BIAS
FET
DRIVER
MODULATOR
INR+
VBATT
2.5V TO 5.0V
INR–
SHUTDOWN
INL+
INL–
GNDGND
10µF
22nF
1
1
INPUT CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY V
DD
/2.
22nF
1
344kΩ
344kΩ
GAIN = 344kΩ/(43kΩ + R
EXT
)
43kΩ
43kΩ
43kΩ
43kΩ
R
EXT
R
EXT
R
EXT
R
EXT
344kΩ
344kΩ
22nF
1
22nF
1
SD
LEFT IN+
LEFT IN–
RIGHT IN–
RIGHT IN+
SSM2306
6542-001
Figure 1.
