MAX9718(2003) Просмотр технического описания (PDF) - Maxim Integrated

Номер в каталоге

Компоненты Описание

производитель

MAX9718
(Rev.:2003)

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

Maxim Integrated 

Low-Cost, Mono/Stereo,

1.4W Differential Audio Power Amplifiers

+1

VOUT(P-P)

RF

RF

2 x VOUT(P-P)

-1

VOUT(P-P)

Figure 1. Bridge-Tied Load Configuration

single-ended amplifiers. These capacitors can be

large, expensive, consume board space, and degrade

low-frequency performance.

Power Dissipation and Heat Sinking

Under normal operating conditions, the MAX9718/

MAX9719 dissipate a significant amount of power. The

maximum power dissipation for each package is given

in the Absolute Maximum Ratings section under

Continuous Power Dissipation or can be calculated by

the following equation:

PDISSPKG(MAX)

=

TJ(MAX) −

θJA

TA

where TJ(MAX) is +150°C, TA is the ambient tempera-

ture, and θJA is the reciprocal of the derating factor in

°C/W as specified in the Absolute Maximum Ratings

section. For example, θJA of the TQFN package is

+59.2°C/W.

The increase in power delivered by the BTL configura-

tion directly results in an increase in internal power dis-

sipation over the single-ended configuration. The

maximum internal power dissipation for a given VCC

and load is given by the following equation:

PDISSPKG(MAX)

=

2VCC2

π2RL

If the internal power dissipation for a given application

exceeds the maximum allowed for a given package,

reduce power dissipation by increasing the ground

plane heat-sinking capability and the size of the traces

to the device (see the Layout and Grounding section).

Other methods for reducing power dissipation are to

reduce VCC, increase load impedance, decrease ambi-

ent temperature, reduce gain, or reduce input signal.

Thermal-overload protection limits total power dissipa-

tion in the MAX9718/MAX9719. When the junction tem-

perature exceeds +160°C, the thermal protection

INVERTING

RIN

DIFFERENTIAL

INPUT (OPTIONAL)

MAX9718A

MAX9719A

IN-

BIAS

GENERATOR

OUT+

OUT-

NONINVERTING

RIN

IN+

DIFFERENTIAL

INPUT (OPTIONAL)

Figure 2. Setting the MAX9718A/MAX9719A Gain

circuitry disables the amplifier output stage. The ampli-

fiers are enabled once the junction temperature cools

by 15°C. A pulsing output under continuous thermal

overload results as the device heats and cools.

For optimum power dissipation and heat sinking, con-

nect the exposed pad found on the µMAX, TDFN,

TQFN, and TSSOP packages to a large ground plane.

Fixed Differential Gain

The MAX9718B, MAX9718C, MAX9718D, MAX9719B,

MAX9719C, and MAX9719D feature internally fixed

gains (see the Selector Guide). This simplifies design,

decreases required footprint size, and eliminates exter-

nal gain-setting resistors. Resistors R1 and R2 shown in

the Typical Operating Circuit are used to achieve each

fixed gain.

Adjustable Differential Gain

Gain-Setting Resistors

External feedback resistors set the gain of the

MAX9718A and MAX9719A. Resistors RF and RIN

(Figure 2) set the gain of the amplifier as follows:

AV

=

RF

RIN

where AV is the desired voltage gain. Hence, an RIN of

10kΩ and an RF of 20kΩ yields a gain of 2V/V, or 6dB.

RF can be either fixed or variable, allowing the use of a

digitally controlled potentiometer to alter the gain under

software control.

______________________________________________________________________________________ 11

Share Link: