SSM2211_04 데이터 시트보기 (PDF) - Analog Devices

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SSM2211_04

Low Distortion 1.5 Watt Audio Power Amplifier

Analog Devices 

SSM2211

0.35

0.30

VDD = 5V

RL = 4Ω

0.25

0.20

0.15

RL = 8Ω

0.10

0.05

RL = 16Ω

0

0

0.1

0.2

0.3

0.4

OUTPUT POWER (W)

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

with VDD = 5 V

The maximum power dissipation for a single-ended output is

PDISS , MAX

=

VDD 2

2 π2RL

(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 other competitors’ equivalent 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 other

competitors’ devices.

The SSM2211 is also capable of providing amplification even at

supply voltages as low as 1.7 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 bridged-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).

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.

1.6

1.4

1.2

RL = 4Ω

1.0

RL = 8Ω

0.8

0.6

RL = 16Ω

0.4

0.2

0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

SUPPLY VOLTAGE (V)

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.

Pin 1 should be connected 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 could 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.

R8

VDD

C2

VIN

VDD

R5

R6

–

OP181

A2

+

R1

R3

R2

R7

VDD

R4

D1

C1

4

5

SSM2211

1

8

A1

NOTE

ADDITIONAL PINS OMITTED FOR CLARITY

Figure 47. Automatic Shutdown Circuit

Rev. C | Page 16 of 20

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