SSM2211CP-R2 datasheet(17/24 Pages) AD

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SSM2211

Rev. D | Page 17 of 24

OUTPUT POWER (W)

0.35

0.30

0.4

0.1

0.2

0.3

0.20

0.15

0.10

0.05

0.25

VDD = 5V

RL = 4Ω

RL = 8Ω

RL = 16Ω

Figure 45. Power Dissipation vs. Single-Ended Output Power

with VDD = 5 V

The maximum power dissipation for a single-ended output is

MAX

DISS

(11)

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.

SUPPLY VOLTAGE (V)

1.5

5.0

2.0

2.5

3.0

3.5

4.0

4.5

1.6

1.0

0.8

0.4

0.2

1.4

1.2

0.6

RL = 4

RL = 8

RL = 16

Figure 46. Maximum Output Power vs. VSY

Shutdown Feature

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 VDD mutes the outputs and puts the device into shutdown

mode. A pull-up or pull-down resistor is not required. Pin 1

should always be connected to a fixed potential, either VDD or

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.

SSM2211

VIN

VDD

OP181

–

VDD

NOTE

ADDITIONAL PINS OMITTED FOR CLARITY

Figure 47. Automatic Shutdown Circuit

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