Filterless High Efficiency
Mono 3 W Class-D Audio Amplifier
SSM2317
supply. It is capable of delivering 3 W of continuous output
power with <1% THD + N driving a 3 Ω load from a 5.0 V supply.
FEATURES
Filterless Class-D amplifier with Σ-Δ modulation
Automatic level control (ALC) improves dynamic range and
prevents clipping
3 W into 3 Ω load and 1.4 W into 8 Ω load at 5.0 V supply
with <10% total harmonic distortion (ALC off)
700 mW into 8 Ω load at 4.2 V supply (ALC 80%)
93% efficiency at 5.0 V, 1.4 W into 8 Ω speaker
>93 dB signal-to-noise ratio (SNR)
Single-supply operation from 2.5 V to 5.5 V
20 nA ultralow shutdown current
Short-circuit and thermal protection
Available in 9-ball, 1.5 mm × 1.5 mm WLCSP
Pop-and-click suppression
Built-in resistors reduce board component count
Default fixed 18 dB or user-adjustable gain setting
The SSM2317 features a high efficiency, low noise modulation
scheme that does not require any external LC output filters. The
modulation continues to provide high efficiency even at low output
power. It operates with 93% efficiency at 1.4 W into 8 Ω or 85%
efficiency at 3 W into 3 Ω from a 5.0 V supply and has an SNR of
>93 dB. Spread-spectrum pulse density modulation is used to
provide lower EMI radiated emissions compared with other
Class-D architectures.
Automatic level control (ALC) can be activated to suppress
clipping and improve dynamic range. This feature only requires
one external resistor tied to GND via the VTH pin and an
activation voltage on the ALC_EN pin.
The SSM2317 has a micropower shutdown mode with a typical
shutdown current of 20 nA. Shutdown is enabled by applying
APPLICATIONS
Mobile phones
SD
a logic low to the
pin.
MP3 players
The device also includes pop-and-click suppression circuitry. This
minimizes voltage glitches at the output during turn-on and turn-
off, reducing audible noise on activation and deactivation.
Portable gaming
Portable electronics
Educational toys
The default gain of the SSM2317 is 18 dB, but users can reduce the
gain by using a pair of external resistors (see the Gain section).
GENERAL DESCRIPTION
The SSM2317 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
The SSM2317 is specified over the commercial temperature range
of −40°C to +85°C. It has built-in thermal shutdown and output
short-circuit protection. It is available in a 9-ball, 1.5 mm × 1.5 mm
wafer level chip scale package (WLCSP).
FUNCTIONAL BLOCK DIAGRAM
VBATT
2.5V TO 5.5V
10µF
0.1µF
VDD
SSM2317
1
1
80kΩ
0.1µF
10kΩ
10kΩ
IN+
AUDIO IN+
OUT+
OUT–
MODULATOR
FET
DRIVER
(Σ-Δ)
0.1µF
IN–
SD
AUDIO IN–
80kΩ
INTERNAL
OSCILLATOR
POP-AND-CLICK
SUPPRESSION
BIAS
ALC
SHUTDOWN
GND
ALC_EN
VTH
R
TH
ALC ENABLE
1
INPUT CAPACITORS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY V /2.
DD
Figure 1.
Rev. A
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