Filterless High Efficiency
Mono 1.4 W Class-D Audio Amplifier
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Filterless Class-D amplifier with Σ-Δ modulation
No sync necessary when using multiple Class-D amplifiers
from Analog Devices, Inc.
1.4 W into 8 Ω at 5.0 V supply with less than 1% THD + N
85% efficiency at 5.0 V, 1.4 W into 8 Ω speaker
Greater than 98 dB SNR (signal-to-noise ratio)
Single-supply operation from 2.5 V to 5.0 V
20 nA ultralow shutdown current
Short-circuit and thermal protection
Available in 8-lead, 3 mm × 3 mm LFCSP and MSOP packages
Built-in resistors reduce board component count
Fixed and user-adjustable gain configurations
The SSM2301 is a fully integrated, high efficiency, Class-D audio
amplifier 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 5.0 V
supply. It is capable of delivering 1.4 W of continuous output
power with less than 1% THD + N driving an 8 Ω load from
a 5.0 V supply.
The SSM2301 features a high efficiency, low noise modulation
scheme that does not require external LC output filters. The modu-
lation provides high efficiency even at low output power.
The SSM2301 operates with 85% efficiency at 1.4 W into 8 Ω
from a 5.0 V supply and has a signal-to-noise ratio (SNR) that
is greater than 98 dB. Spread-spectrum modulation is used to
provide lower EMI-radiated emissions compared with other
The SSM2301 has a micropower shutdown mode with a maximum
shutdown current of 30 nA. Shutdown is enabled by applying
a logic low to the SD pin.
The device also includes pop-and-click suppression circuitry.
This minimizes voltage glitches at the output during turn-on
and turn-off, thus reducing audible noise on activation and
The fully differential input of the SSM2301 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.
The SSM2301 also has excellent rejection of power supply noise,
including noise caused by GSM transmission bursts and RF
rectification. PSRR is typically 63 dB at 217 Hz.
The gain can be set to 6 dB or 12 dB by utilizing the gain control
select pin connected respectively to ground or to VDD. Gain
can also be adjusted externally by inserting a resistor in series
with each input pin.
The SSM2301 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 both an 8-lead, 3 mm ×
3 mm lead-frame chip scale package (LFCSP) and an 8-lead
FUNCTIONAL BLOCK DIAGRAM
2.5V TO 5.0V
1 INPUT CAPS ARE OPTIONAL IF INPUT DC COMMON-MODE
VOLTAGE IS APPROXIMATELY VDD/2.