ssm2211z-eval Analog Devices, Inc., ssm2211z-eval Datasheet - Page 17

• Manufacturer Part Number: ssm2211z-eval
• Description: Low Distortion 1.5 Watt Audio Power Amplifier
• Manufacturer: Analog Devices, Inc.

The maximum power dissipation for a single-ended output is
OUTPUT VOLTAGE HEADROOM
The outputs of both amplifiers in the SSM2211 can come to
within 400 mV of either supply rail while driving an 8 Ω load.
As compared to equivalent competitor products, the SSM2211
has a higher output voltage headroom. This means that the
SSM2211 can deliver an equivalent maximum output power
while running from a lower supply voltage. By running at a
lower supply voltage, the internal power dissipation of the
device is reduced, as can be seen in Equation 9. This extended
output headroom, along with the LFCSP package, allows the
SSM2211 to operate in higher ambient temperatures than
competitor devices.
The SSM2211 is also capable of providing amplification even at
supply voltages as low as 2.7 V. The maximum power available at
the output is a function of the supply voltage. Therefore, as the
supply voltage decreases, so does the maximum power output
from the device. The maximum output power vs. supply voltage
at various bridge-tied load resistances is shown in Figure 46. The
maximum output power is defined as the point at which the
output has 1% total harmonic distortion (THD + N).
To find the minimum supply voltage needed to achieve a
specified maximum undistorted output power use Figure 46.
For example, an application requires only 500 mW to be
output for an 8 Ω speaker. With the speaker connected in a
bridged-output configuration, the minimum supply voltage
required is 3.3 V.
P
DISS
0.35
0.30
0.25
0.20
0.15
0.10
0.05
Figure 45. Power Dissipation vs. Single-Ended Output Power
0
,
0
MAX
V
=
DD
2
= 5V
V
π
DD
2
R
0.1
2
L
OUTPUT POWER (W)
with V
R
DD
L
0.2
= 16Ω
= 5 V
R
L
0.3
= 8Ω
R
L
= 4Ω
0.4
(11)
Rev. D | Page 17 of 24
The SSM2211 can be put into a low power consumption shut-
down mode by connecting Pin 1 to 5 V. In shutdown mode,
the SSM2211 has an extremely low supply current of less than
10 nA. This makes the SSM2211 ideal for battery-powered
applications.
Connect Pin 1 to ground for normal operation. Connecting Pin 1
to V
mode. A pull-up or pull-down resistor is not required. Pin 1
should always be connected to a fixed potential, either V
ground, and never be left floating. Leaving Pin 1 unconnected
can produce unpredictable results.
AUTOMATIC SHUTDOWN-SENSING CIRCUIT
Figure 47 shows a circuit that can be used to take the SSM2211
in and out of shutdown mode automatically. This circuit can
be set to turn the SSM2211 on when an input signal of a certain
amplitude is detected. The circuit also puts the device into low
power shutdown mode if an input signal is not sensed within
a certain amount of time. This can be useful in a variety of
portable radio applications, where power conservation is critical.
V
IN
DD
V
NOTE
ADDITIONAL PINS OMITTED FOR CLARITY
mutes the outputs and puts the device into shutdown
C2
DD
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.5
R1
V
DD
R5
R6
Figure 46. Maximum Output Power vs. V
Figure 47. Automatic Shutdown Circuit
2.0
R2
OP181
+
–
A2
R3
2.5
Shutdown Feature
SUPPLY VOLTAGE (V)
3.0
R7
D1
V
DD
3.5
R4
C1
RL = 4Ω
4.0
4
1
SY
SSM2211
SSM2211
RL = 16Ω
4.5
RL = 8Ω
R8
A1
DD
5.0
5
8
or