max9752aetit Maxim Integrated Products, Inc., max9752aetit Datasheet - Page 21

• Manufacturer Part Number: max9752aetit
• Description: 2.2w, Low-emi, Stereo, Class D Power Amplifiers With Directdrive Headphone Amplifiers
• Manufacturer: Maxim Integrated Products, Inc.

Figure 11. MAX9752 Beep Summing Circuit
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.
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.
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
8Ω speakers exhibit series inductances in the 30µH to
100µH range. Highest efficiency is achieved with speak-
er inductances > 60µH.
2.2W, Low-EMI, Stereo, Class D Power Amplifiers
Applications Information
MAX9750/MAX9751/MAX9755
______________________________________________________________________________________
Click-and-Pop Suppression
SOURCE 1
SOURCE 2
SOURCE 3
with DirectDrive Headphone Amplifiers
0.47μF
0.47μF
0.47μF
Filterless Operation
Compatibility with
47kΩ
47kΩ
47kΩ
R
R
R
S1
S2
S3
BEEP
BIAS
47kΩ
R
INT
(0.4V
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.
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 V
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.
Figure 12. THD+N vs. P
In- and Out-of-Phase
(300Hz THRESHOLD)
FREQUENCY
V
P-P
DETECTOR
DETECTOR
OUT(BEEP)
WINDOW
THRESHOLD)
Power Dissipation and Heat Sinking
Headphone Amplifier Output Power
0.001
1000
0.01
100
0.1
10
1
SS
0
V
R
A
. In typical stereo audio applications, the
DD
L
V
= 16Ω
= 3dB
= 5V
25
SPEAKER/HEADPHONE
OUT
AMPLIFIER INPUTS
MAX9752
OUTPUTS IN-PHASE
OUTPUT POWER (mW)
50
OUTPUTS 180° OUT-OF-PHASE
with Headphone Output Signals
75
100
125
150
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