Filterless, High Efficiency,
Mono 3 W Class-D Audio Amplifier
SSM2315
Rev. A
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FEATURES
Filterless Class-D amplifier with Σ-Δ modulation
No sync necessary when using multiple Class-D amplifiers
from Analog Devices, Inc.
3 W into 3 Ω load and 1.4 W into 8 Ω load at 5.0 V supply
with <1% total harmonic distortion (THD + N)
93% efficiency at 5.0 V, 1.4 W into 8 Ω speaker
>103 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 6 dB or user adjustable gain setting
APPLICATIONS
Mobile phones
MP3 players
Portable gaming
Portable electronics
Educational toys
GENERAL DESCRIPTION
The SSM2315 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 3 W of continuous output power
with <1% THD + N driving a 3 Ω load from a 5.0 V supply.
The SSM2315 features a high efficiency, low noise modulation
scheme that requires no 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 >103 dB.
Spread-spectrum pulse density modulation is used to provide
lower EMI-radiated emissions compared with other Class-D
architectures.
The SSM2315 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 device also includes pop-and-click suppression circuitry.
This suppression circuitry minimizes voltage glitches at the
output during turn-on and turn-off, reducing audible noise
on activation and deactivation.
The fully differential input of the SSM2315 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 default gain of the SSM2315 is 6 dB, but users can reduce the
gain by using a pair of external resistors (see the Gain section).
The SSM2315 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 9-ball, 1.5 mm × 1.5 mm
wafer level chip scale package (WLCSP).
FUNCTIONAL BLOCK DIAGRAM
SHUTDOWN
0.1µF
VDD
POP/CLICK
SUPPRESSION
OUT+
OUT–
IN+
VBATT
2.5V TO 5.5V
IN–
MODULATOR
(Σ-Δ)
GND
10µF
47nF*
*INPUT CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY V
DD
/2.
47nF*
SD
AUDIO IN–
AUDIO IN+
SSM2315
80kΩ
160kΩ
160kΩ
80kΩ
FET
DRIVER
BIAS
INTERNAL
OSCILLATOR
6857-001
Figure 1.
