2 W, Filterless, Class-D
Stereo Audio Amplifier
SSM2306
The SSM2306 features 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. PDM modulation offers lower
EMI radiated emissions compared to other Class-D architectures.
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 SNR (signal-to-noise ratio)
Available in 16-lead, 3 mm × 3 mm LFCSP
Single-supply operation from 2.5 V to 5.0 V
20 nA ultralow shutdown current
The SSM2306 has a micropower shutdown mode with a typical
shutdown current of 20 nA. Shutdown is enabled by applying a
SD
logic low to the
pin.
Short-circuit and thermal protection
Pop-and-click suppression
Built-in resistors reduce board component count
Default fixed 18 dB gain and user-adjustable
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 VDD/2.
APPLICATIONS
Mobile phones
MP3 players
Portable gaming
Portable electronics
Educational toys
Notebook computers
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.
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% THD + N driving a 4 Ω load from a 5.0 V supply.
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
VBATT
2.5V TO 5.0V
10µF
0.1µF
VDD
SSM2306
344kΩ
VDD
1
1
22nF
22nF
R
R
EXT
EXT
43kΩ
OUTR+
RIGHT IN+
RIGHT IN–
FET
DRIVER
INR+
INR–
MODULATOR
OUTR–
43kΩ
344kΩ
BIAS
INTERNAL
OSCILLATOR
SHUTDOWN
SD
344kΩ
1
1
22nF
22nF
R
R
EXT
EXT
43kΩ
43kΩ
OUTL+
OUTL–
LEFT IN+
LEFT IN–
FET
INL+
INL–
MODULATOR
GND
DRIVER
GND
344kΩ
GAIN = 344kΩ/(43kΩ + R
)
EXT
1
INPUT CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY V /2.
DD
Figure 1.
Rev. 0
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