2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
MAX9750A
VOLUME CONTROL TRANSFER FUNCTION
MAX9750B
VOLUME CONTROL TRANSFER FUNCTION
20
10
20
10
GAIN1 = GAIN2 = 0
GAIN1 = GAIN2 = 0
0
0
SPEAKER MODE
SPEAKER MODE
-10
-20
-30
-40
-50
-60
-70
-80
-10
-20
-30
-40
-50
-60
-70
-80
AUDIO
TAPER
AUDIO
TAPER
HEADPHONE MODE
HEADPHONE MODE
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
V
V
VOL
VOL
Figure 7a. Volume Control Transfer Function
Figure 7b. Volume Control Transfer Function
Headphone Amplifier
MAX9750C
In conventional single-supply headphone amplifiers,
the output-coupling capacitor is a major contributor of
audible clicks and pops. Upon startup, the amplifier
charges the coupling capacitor to its bias voltage, typi-
cally half the supply. Likewise, during shutdown, the
capacitor is discharged to GND. A DC shift across the
capacitor results, which in turn appears as an audible
transient at the speaker. Since the MAX9750/MAX9751/
MAX9755 do not require output-coupling capacitors, no
audible transient occurs.
VOLUME CONTROL TRANSFER FUNCTION
20
GAIN1 = GAIN2 = 0
10
0
-10
SPEAKER MODE
-20
AUDIO
TAPER
-30
-40
-50
HEADPHONE MODE
-60
Additionally, the MAX9750/MAX9751/MAX9755 features
extensive click-and-pop suppression that eliminates
any audible transient sources internal to the device.
The Power-Up/Down Waveform in the Typical
Operating Characteristics shows that there are minimal
spectral components in the audible range at the output
upon startup and shutdown.
-70
-80
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
V
VOL
Figure 7c. Volume Control Transfer Function
R
S1
0.47µF
0.47µF
0.47µF
47kΩ
R
INT
SOURCE 1
SOURCE 2
SOURCE 3
47kΩ
R
S2
47kΩ
SPEAKER/HEADPHONE
AMPLIFER INPUTS
BEEP
V
OUT(BEEP)
WINDOW
R
S3
47kΩ
DETECTOR
(0.3V THRESHOLD)
P-P
MAX9750
FREQUENCY
DETECTOR
BIAS
(300Hz THRESHOLD)
Figure 8. Beep Input
1± ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
