Detailed Description

The MAX9710/MAX9711 are 3W BTL speaker ampli-

fiers. The MAX9710 is a stereo speaker amplifier, while

the MAX9711 is a mono speaker amplifier. Both

devices feature a low-power shutdown mode, MUTE

mode, and comprehensive click-and-pop suppression.

These devices consist of high output-current op amps

configured as BTL amplifiers (see Functional Diagram).

BIAS

These devices operate from a single 5V supply and

feature an internally generated, power-supply-indepen-

dent, common-mode bias voltage of 2.5V referenced to

ground. BIAS provides both click-and-pop suppression

and sets the DC bias level for the audio outputs. BIAS

is internally connected to the noninverting input of each

speaker amplifier (see Functional Diagram). Choose

the value of the bypass capacitor as described in the

BIAS Capacitor section. No external load should be

applied to BIAS. Any load lowers the BIAS voltage,

affecting the overall performance of the device.

Shutdown

The MAX9710/MAX9711 feature a 0.5µA low-power shut-

down mode that reduces quiescent current consump-

tion. Pulling SHDN low disables the device’s bias

circuitry, the amplifier outputs are actively pulled low,

normal operation.

MUTE

Both devices feature a clickless/popless MUTE mode.

When the device is muted, the input disconnects from

the amplifier. MUTE only affects the power amplifiers

and does not shut down the device. Drive MUTE high to

mute the device. Drive MUTE low for normal operation.

Click-and-Pop Suppression

The MAX9710/MAX9711 feature Maxim’s patented com-

prehensive click-and-pop suppression. During startup,

the common-mode bias voltage of the amplifiers slowly

ramps to the DC bias point using an S-shaped wave-

form. When entering shutdown, the amplifier outputs are

actively driven low simultaneously. This scheme mini-

mizes the energy present in the audio band.

For optimum click-and-pop suppression, choose:

Ω.

Applications Information

BTL Amplifier

The MAX9710/MAX9711 are designed to drive a load

differentially, a configuration referred to as 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 voltage compared to a single-

ended amplifier under similar conditions. Thus, the dif-

ferential gain of the device is twice the closed-loop gain

of the input amplifier. The effective gain is given by:

ing equations yields four times the output power due to

doubling of the output voltage:

Since the differential outputs are biased at midsupply,

there is no net DC voltage across the load. This elimi-

nates the need for DC-blocking capacitors required for

single-ended amplifiers. These capacitors can be

large, expensive, consume board space, and degrade

low-frequency performance.

P

V

R

OUT

RMS

L

=

2

V

V

RMS

OUT P P

=

−

()

22

A

R

R

VD

F

IN

=×

2

3W Mono/Stereo BTL Audio Power Amplifiers

with Shutdown

_______________________________________________________________________________________

7

+1

-1

Figure 1. Bridge-Tied Load Configuration