MAX9719(2003) Просмотр технического описания (PDF) - Maxim Integrated

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MAX9719
(Rev.:2003)

Low-Cost, Mono/Stereo, 1.4W Differential Audio Power Amplifiers

Maxim Integrated 

Low-Cost, Mono/Stereo,

1.4W Differential Audio Power Amplifiers

Pin Description (continued)

MAX9718

TDFN/

µMAX

UCSP

—

—

—

—

—

—

EP

—

PIN

MAX9719

TQFN UCSP TSSOP

NAME

FUNCTION

12

D4

14

OUTR+ Right-Channel Bridge Amplifier Positive Output

15

D2

1

OUTR- Right-Channel Bridge Amplifier Negative Output

16

D1

2

INR- Right-Channel Noninverting Input

EP

—

EP

EP Exposed Pad. Connect EP to GND.

Detailed Description

The MAX9718/MAX9719 are 1.4W BTL speaker ampli-

fiers. The MAX9718 is a mono speaker amplifier, while

the MAX9719 is a stereo speaker amplifier. Both

devices feature a low-power shutdown mode, and

industry-leading click-and-pop suppression. The

MAX9718 features a two-input shutdown scheme to

configure shutdown for active high or active low. These

devices consist of high output-current audio amps con-

figured as BTL amplifiers (see the Functional Diagrams).

Both adjustable and fixed gain (0dB, 3dB, 6dB) versions

are available.

BIAS

These devices operate from a single 2.7V to 5.5V sup-

ply and feature an internally generated, common-mode

bias voltage of VCC/ 2 referenced to ground. BIAS pro-

vides both click-and-pop suppression and sets the DC

bias level for the audio outputs. Choose the value of the

bypass capacitor as described in the BIAS Capacitor

section. Do not connect external loads to BIAS as this

can affect the overall performance.

Shutdown Mode

The MAX9718/MAX9719 feature a 100nA low-power

shutdown mode that reduces quiescent current con-

sumption. Entering shutdown disables the device’s bias

circuitry, the amplifier outputs go high impedance, and

BIAS is driven to GND. The MAX9718 SHDM input con-

trols the polarity of SHDN. Drive SHDM high for an

active-high SHDN input. Drive SHDM low for an active-

low SHDN input (see Table 1). The MAX9719 features

an active-low shutdown input, SHDN.

Click-and-Pop Suppression

The MAX9718/MAX9719 feature Maxim’s industry-lead-

ing click-and-pop suppression circuitry. During startup,

the amplifier common-mode bias voltage ramps to the

DC bias point. When entering shutdown, the amplifier

outputs are high impedance to 100kΩ between both

outputs. This scheme minimizes the energy present in

the audio band.

Table 1. Shutdown Mode Selection

(MAX9718 Only)

SHDM

0

0

1

1

SHDN

0

1

0

1

OPERATIONAL MODE

Shutdown

Normal operation

Normal operation

Shutdown

Applications Information

BTL Amplifier

The MAX9718/MAX9719 are designed to drive a load

differentially, a configuration referred to as bridge-tied

load or 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 differential gain of the device is twice the

closed-loop gain of the input amplifier. The effective

gain is given by:

AVD

=

2

×

RF

RIN

Substituting 2 x VOUT(P-P) for VOUT(P-P) into the following

equations yields four times the output power due to

doubling of the output voltage:

VRMS = VOUT(P−P)

22

POUT

=

VRMS2

RL

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

10 ______________________________________________________________________________________

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