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SSM2211_02

Low Distortion 1.5 Watt Audio Power Amplifier

Analog Devices 

SSM2211

–50 TA = 25؇C

VDD = 5V ؎ 100mV

CB = 15 mF

–55 AVD = 2

–60



–65

–70

20

100

1k

FREQUENCY – Hz

10k 30k

TPC 37. PSRR vs. Frequency

PRODUCT OVERVIEW

The SSM2211 is a low distortion speaker amplifier that can run

from a 1.7 V to 5.5 V supply. It consists of a rail-to-rail input

and a differential output that can be driven within 400 mV of

either supply rail while supplying a sustained output current of

350 mA. The SSM2211 is unity-gain stable, requiring no exter-

nal compensation capacitors, and can be configured for gains of

up to 40 dB. Figure 1 shows the simplified schematic.

20k⍀

VDD

6

20k⍀

VIN

4

3

A1

SSM2211

5

VO1

50k⍀

50k⍀

50k⍀

2

A2

8

VO2

0.1␮F

50k⍀

BIAS

CONTROL

7

1

SHUTDOWN

Figure 1. Simplified Schematic

Pin 4 and Pin 3 are the inverting and noninverting terminals to A1.

An offset voltage is provided at Pin 2, which should be connected

to Pin 3 for use in single supply applications. The output of A1

appears at Pin 5. A second op amp, A2, is configured with a fixed

gain of AV = –1 and produces an inverted replica of Pin 5 at Pin 8.

The SSM2211 outputs at Pins 5 and 8 produce a bridged configu-

ration output to which a speaker can be connected. This bridge

configuration offers the advantage of a more efficient power trans-

fer from the input to the speaker. Because both outputs are sym-

metric, the dc bias at Pins 5 and 8 are exactly equal, resulting in

zero dc differential voltage across the outputs. This eliminates the

need for a coupling capacitor at the output.

Thermal Performance—SOIC

The SSM2211 can achieve 1 W continuous output into 8 W in

SOIC, even at ambient temperatures up to 85∞C. This is due to a

proprietary SOIC package from Analog Devices that makes use of

an internal structure called a Thermal Coastline. The Thermal

Coastline provides a more efficient heat dissipation from the die

than in standard SOIC packages. This increase in heat dissipation

allows the device to operate in higher ambient temperatures or at

higher continuous output currents without overheating the die.

For a standard SOIC package, typical junction to ambient

temperature thermal resistance (␪JA) is 158∞C/W. In a Thermal

Coastline SOIC package, ␪JA is 98∞C/W. Simply put, a die in a

Thermal Coastline package will not get as hot as a die in a stan-

dard SOIC package at the same current output.

Because of the large amounts of power dissipated in a speaker

amplifier, competitor’s parts operating from a 5 V supply can

only drive 1 W into 8 W in ambient temperatures less than

44∞C, or 111∞F. With the Thermal Coastline SOIC package, the

SSM2211 can drive an 8 W speaker with 1 W from a 5 V supply

with ambient temperatures as high as 85∞C (185∞F), without a

heat sink or forced air flow.

Thermal Performance—LFCSP

The addition of the LFCSP to the Analog Devices’ package

portfolio offers the SSM2211 user even greater choice when

considering thermal performance criteria. For the 8-lead 3 mm

ϫ 3 mm LFCSP the ␪JA is 50∞C/W. This is a significant perfor-

mance improvement over most other packaging options and even

betters the thermal performance of the SOIC with Thermal

Coastline lead frame.

–8–

REV. B

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