MAX9752 datasheet(21/29 Pages) MAXIM

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Click-and-Pop Suppression

The MAX9752/MAX9753/MAX9754 feature Maxim’s

comprehensive, industry-leading click-and-pop sup-

pression eliminating audible transients at startup. The

Turn-On and Turn-Off Response waveforms in the

Typical Operating Characteristics show that there are

minimal spectral components in the audible range at

the output upon startup and shutdown.

Applications Information

Compatibility with

MAX9750/MAX9751/MAX9755

The MAX9752/MAX9753/MAX9754 provide a high-effi-

ciency, Class D speaker driver with very low EMI (see

the Typical Operating Characteristics). If a Class AB

output is desired, the MAX9750/MAX9751/MAX9755

can be substituted. The MAX9750, MAX9751, and

MAX9755 are pin-for-pin compatible with the MAX9752,

MAX9753, and MAX9754, respectively.

Filterless Operation

The MAX9752/MAX9753/MAX9754 do not require an

output filter in most applications. The devices rely on

the inherent inductance of the speaker coil and the nat-

ural filtering of both the speaker and the human ear to

recover the audio component of the square-wave out-

put. Eliminating the output filter results in a smaller, less

costly, more efficient solution.

Voice coil movement due to the square-wave frequency

is very small because the switching frequency is well

beyond the bandwidth of speakers. Although this move-

ment is small, a speaker not designed to handle the

additional power can be damaged. Use a speaker with a

series inductance > 30µH for optimum results. Typical

Ω speakers exhibit series inductances in the 30µH to

100µH range. Highest efficiency is achieved with speak-

er inductances > 60µH.

Power Dissipation and Heat Sinking

Because the MAX9752/MAX9753/MAX9754 have high-

efficiency, Class D speaker drivers, the intrinsic pack-

age power dissipation capabilities are sufficient for

cooling. No special heatsinking is needed in normal

operating conditions.

Headphone Amplifier Output Power

The headphone amplifiers have been specified for the

worst-case scenario—when both inputs are in-phase.

Under this condition, the drivers simultaneously draw cur-

rent from the charge pump, leading to a slight loss in

headroom of VSS. In typical stereo audio applications, the

left and right signals have differences in both magnitude

and phase, subsequently leading to an increase in the

maximum attainable output power. Figure 12 shows the

two cases for in- and out-of-phase. In reality, the available

power lies between these extremes.

2.2W, Low-EMI, Stereo, Class D Power Amplifiers

with DirectDrive Headphone Amplifiers

______________________________________________________________________________________

MAX9752

RS3

47k

BEEP

0.47

μF

SOURCE 3

RS2

47k

0.47

μF

SOURCE 2

RS1

47k

0.47

μF

SOURCE 1

RINT

47k

BIAS

WINDOW

DETECTOR

(0.4VP-P THRESHOLD)

FREQUENCY

DETECTOR

(300Hz THRESHOLD)

SPEAKER/HEADPHONE

AMPLIFIER INPUTS

VOUT(BEEP)

Figure 11. MAX9752 Beep Summing Circuit

OUTPUT POWER (mW)

125

100

0.01

0.1

100

1000

0.001

0150

VDD = 5V

RL = 16

AV = 3dB

OUTPUTS IN-PHASE

OUTPUTS 180

° OUT-OF-PHASE

Figure 12. THD+N vs. POUT with Headphone Output Signals

In- and Out-of-Phase

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