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SSM2250RM-SSM2250RU
Mono 1.5 W/Stereo 250 mW Power Amplifier
REV.0
Mono 1.5 W/Stereo 250 mW
Power Amplifier
PIN CONFIGURATIONS
10-Lead MSOP
(RM Suffix)
FEATURES
Part of SoundMax® Audio Solution for Desktop Computers
Mono 1.5 W Differential or Stereo 250 mW Output
Single-Supply Operation: 2.7 V to 6 V
Low Shutdown Current = 60 mA
PC 99 Compliant
Low Distortion: 0.2% THD at 1.5 W
Wide Bandwidth: 4 MHz
Unity-Gain Stable
APPLICATIONS
Desktop, Portable or Palmtop Computers
Sound Cards
Communication Headsets
2-Way Communications
Handheld Games
GENERAL DESCRIPTIONThe SSM2250 is intended for use in desktop computers that have
basic audio functions. It is also ideal for any audio system that needs
to provide both an internal monaural speaker and a stereo line or
headphone output. Combined with an AC’97 Codec it provides a
PC audio system that meets the PC 99 requirements. The SSM2250
is compact and requires a minimum of external components.
The SSM2250 features an audio amplifier capable of delivering
1.5 W of low distortion power into a mono 4 W bridged-tied load
(BTL) or 2 3 90 mW into stereo 32 W single-ended load (SE)
headphones. Both amplifiers provide rail-to-rail outputs for maxi-
mum dynamic range from a single supply. The balanced output
provides maximum output from 5 V supply and eliminates the
need for a coupling capacitor.
The SSM2250 can automatically switch between an internal
mono speaker and external headphones. The device can run from
a single supply, ranging from 2.7 V to 6 V, with an active supply
current of 9␣mA typical. The ability to shut down the amplifiers,
(60 mA shutdown current) makes the SSM2250 an ideal speaker
amplifier for battery-powered applications.
The SSM2250 is specified over the industrial (–40°C to +85°C)
temperature range. It is available in 14-lead TSSOP and 10-lead
MSOP surface mount packages.
Figure 1.Functional Block Diagram
SoundMax is a registered trademark of Analog Devices, Inc.
14-Lead TSSOP
(RU Suffix)
SSM2250–SPECIFICATIONS
ELECTRICAL CHARACTERISTICSSHUTDOWN INPUT
Specifications subject to change without notice.
(VS = 5.0 V, VCM = 2.5 V, TA = 258C unless otherwise noted)
ELECTRICAL CHARACTERISTICSSHUTDOWN INPUT
Specifications subject to change without notice.
(VS = 2.7 V, VCM = 1.35 V, TA = 258C unless otherwise noted)
ABSOLUTE MAXIMUM RATINGSSupply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 V
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . .–5 V
Common-Mode Input Voltage . . . . . . . . . . . . . . . . . . . .–6 V
ESD Susceptibility . . . . . . . . . . . . . . . . . . . . . . . . . . . .2000 V
Storage Temperature Range
RM, RU Packages . . . . . . . . . . . . . . . . . .–65°C to +150°C
Operating Temperature Range
SSM2250 . . . . . . . . . . . . . . . . . . . . . . . . . .–40°C to +85°C
Junction Temperature Range
RM, RU Packages . . . . . . . . . . . . . . . . . .–65°C to +165°C
Lead Temperature Range (Soldering, 60 sec) . . . . . . . .300°C
NOTESStresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating condi-
tions for extended periods may affect device reliability.Differential Input Voltage or –VS, whichever is lower.
NOTEqJA is specified for worst-case conditions, i.e., qJA is specified for device soldered
in circuit board for surface mount packages.
CAUTIONESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the SSM2250 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
ORDERING GUIDE
SSM2250
FREQUENCY –Hz
TOTAL HARMONIC DISTORTION – %20k1001k10kFigure 2.BTL Out THD + N vs. Frequency
20k1001k10k
FREQUENCY –Hz
TOTAL HARMONIC DISTORTION – %Figure 3.BTL Out THD + N vs. Frequency
OUTPUT POWER – W
0.110m2100m
TOTAL HARMONIC DISTORTION –Figure 4.THD + N vs. Output Power
FREQUENCY – Hz
0.012020k100
TOTAL HARMONIC DISTORTION – %
10kFigure 5.SE Out THD + N vs. Frequency
FREQUENCY – Hz
0.012020k100
TOTAL HARMONIC DISTORTION – %
10kFigure 6.SE Out THD + N vs. Frequency
OUTPUT POWER – mW
TOTAL HARMONIC DISTORTION – %
0.1Figure 7.BTL Out THD + N vs. Output Power
OUTPUT POWER – W
10m2100m
TOTAL HARMONIC DISTORTION –Figure 8.BTL Out THD + N vs. Output Power at 20 Hz
OUTPUT POWER – W
0.110m2100m
TOTAL HARMONIC DISTORTION –Figure 9.BTL Out THD + N vs. Output Power at 20 kHz
Figure 10.SE Out THD + N vs. Output Power at 20 Hz
Figure 11.SE Out THD + N vs. Output Power at 20 kHz
SSM2250
PRODUCT OVERVIEWThe SSM2250 is a low distortion power amplifier that can drive a
set of stereo headphones or a single 8 W loudspeaker. It contains
three rail-to-rail output op amps, click and pop reduction biasing,
and all necessary switching circuitry. In SE (Single-Ended) Mode,
the device automatically mutes the internal 8 W speaker. In BTL
(Bridge-Tied Load) Mode, the internal speaker is activated.
The SSM2250 can operate from a 2.7 V to 5.5 V single supply.
The rail-to-rail outputs can be driven to within 400 mV of either
supply rail while supplying a sustained output current of 350 mA
into 8 W. The device is unity-gain stable and requires no exter-
nal compensation capacitors. The SSM2250 can be configured
for gains of up to 40␣dB.
TYPICAL APPLICATIONIn SE Mode, the device operates similar to a high current output,
dual op amp. A1 and A3 are independent amplifiers with a gain of
–R2/R1. The outputs of A1 and A3 are used to drive the external
headphones plugged into the headphone jack. Amplifier A2 is shut
down to a high output impedance state. This prevents current from
flowing through the 8 W internal speaker, thereby muting it.
Although the gains of A1 and A3 can be set independently, it is
recommended that the feedback and feedforward resistor around
both amplifiers be equal. This will prevent one channel from
becoming louder than the other.
In BTL mode, the current into the Right In pin is directed to
the input of A1. This effectively sums the Left and Right In
audio signals. The A2 amplifier is activated and configured with
a fixed gain of AV␣=␣–1. This produces a balanced output con-
figuration that drives the internal speaker. Because the BTL
output voltages swing opposite to each other, the gain to the
speaker in BTL mode is twice the gain of SE mode. The voltage
across the internal speaker can be written:
The bridged output configuration offers the advantage of a more
efficient power transfer from the input to the speaker. Because
both outputs are symmetric, the dc voltage bias across the 8 W
internal speaker is zero. This eliminates the need for a coupling
capacitor at the output. In BTL mode, the A3 amplifier is shut
down to conserve power.
In BTL Mode, the SSM2250 can achieve 1␣W continuous output
into 8␣W at ambient temperatures up to 40°C. The power derating
curve shown in Figure 15 should be observed for proper operation at
higher ambient temperatures. For a standard 14-lead TSSOP pack-
age, typical junction-to-ambient temperature thermal resistance (qJA)
is 180°C/W on a 2-layer board, and 140°C/W on a 4-layer board.
Internal Speaker/External Headphones Automatic SwitchingPin 4 on the SSM2250 controls the switching between BTL and
SE Modes. Logic low to Pin 4 activates BTL Mode, while logic
high activates SE Mode. The configuration shown in Figure 12
provides the appropriate logic voltages to Pin 4, muting the
internal speaker when headphones are plugged into the jack.
A stereo headphone jack with a normalizing pin is required for
the application. With no plug inserted, a mechanical spring
connects the normalizing pin to the output pin in the jack.
Once a plug is inserted, this connection is broken.
Referring to Figure 12, Pin 4 of the SSM2250 is connected to the
normalizing pin for the right channel output. This is the pin in
the headphone jack that will hit the ring on the headphone plug.
A 100 kW pull-up resistor to 5 V is also connected at this point.
With a headphone plug inserted, the normalizing pin disconnects
from the output pin, and Pin 4 is pulled up to 5 V, activating SE
Mode on the SSM2250. This mutes the internal speaker while
driving the stereo headphones.
Once the headphone plug is removed, the normalizing pin con-
nects to the output pin. This drives the voltage at Pin 4 to 50 mV,
as this point is pulled low by the 1 kW resistor now connected to
the node. The SSM2250 goes into BTL mode, deactivating the
right SE amplifier to prevent the occurrence of any false mode
switching.
It is important to connect Pin 4 and the 100 kW pull up resistor
to the normalizing pin for the right output in the headphone
jack. Connecting them to the left output normalizing pin will
result in improper operation from the device. The normalizing
pin to the left output in the headphone jack should be left open.
Coupling CapacitorsOutput coupling capacitors are not required to drive the internal
speaker from the BTL outputs. However, coupling capacitors are
required between the amplifier’s SE outputs and the headphone
jack to drive external headphones. This prevents dc current from
flowing through the headphone speakers, whose resistances are
typically on the order of 80 W.
LEFT IN
20kV
SHUTDOWN
RIGHT IN
220mF
