330mW, Ultra-Small, Audio Power Amplifiers

with Shutdown

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9

Pin Description

PIN/BUMP

TDFN

UCSP

NAME

FUNCTION

1

C3

SHDN

Active-High Shutdown. Connect SHDN to GND for normal operation.

2

C1

BIAS

capacitor from BIAS to GND.

3

A3

IN+

Noninverting Input

4

A1

IN-

Inverting Input

5

A2

OUT+

Bridged Amplifier Positive Output

6B3

Power Supply

7

B1

GND

Ground

8

C2

OUT-

Bridged Amplifier Negative Output

EP

—

EP

Exposed Paddle. Connect exposed pad to GND.

Detailed Description

The MAX4366/MAX4367/MAX4368 bridged audio

power amplifiers can deliver 330mW into a 32

Ω load, or

200mW into a 16

Ω load, while operating from a single

5V supply. These devices consist of two high-output-

current op amps configured as a bridge-tied load (BTL)

amplifier (see

Functional Diagram). The closed-loop

gain of the input op amp sets the single-ended gain of

the device. Two external resistors set the gain of the

MAX4366 (see

Gain-Setting Resistors section). The

MAX4367/MAX4368 feature internally fixed gains of

2V/V and 3V/V, respectively. The output of the first

amplifier serves as the input to the second amplifier,

which is configured as an inverting unity-gain follower

in all three devices. This results in two outputs, identical

in magnitude, but 180° out of phase.

BIAS

The MAX4366/MAX4367/MAX4368 feature an internally

enced to GND. BIAS provides both click-and-pop sup-

pression and the DC bias level for the audio signal.

BIAS is internally connected to the noninverting input of

one amplifier, and should be connected to the nonin-

verting input of the other amplifier for proper signal

biasing (

Typical Application Circuit). Choose the value

of the bypass capacitor as described in the

BIAS

Capacitor section.

Shutdown

The MAX4366/MAX4367/MAX4368 feature a 35µA, low-

power shutdown mode that reduces quiescent current

consumption and extends battery life. Pulling SHDN

high disables the device’s bias circuitry and drives

OUT+, OUT-, and BIAS to GND. Connect SHDN to

GND for normal operation.

Applications Information

Bridge-Tied Load

The MAX4366/MAX4367/MAX4368 are designed to

drive a load differentially, a configuration referred to as

bridge-tied load (BTL). The BTL configuration (Figure 1)

offers advantages over the single-ended configuration,

where one side of the load is connected to ground.

Driving the load differentially doubles the output volt-

age compared to a single-ended amplifier under similar

conditions. The differential gain of the device is twice

the closed-loop gain of the input amplifier. The effective

gain of the MAX4366 is given by:

A

R

R

VD

F

IN

=×

2

+1

R

L

OUT+

2 x OUT

OUT-

-1

Figure 1. Bridge-Tied Load Configuration