max9758etjt Maxim Integrated Products, Inc., max9758etjt Datasheet - Page 20

• Manufacturer Part Number: max9758etjt
• Description: 2.3w Stereo Speaker Amplifiers And Directdrive Headphone Amplifiers With Automatic Level Control
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9756/MAX9757/MAX9758 feature an internally
generated, power-supply independent, common-mode
bias voltage of 2.5V referenced to GND. BIAS provides
both click-and-pop suppression and sets the DC bias
level for the amplifiers. Choose the value of the bypass
capacitor as described in the BIAS Capacitor section.
No external load should be applied to BIAS. Any load
lowers the BIAS voltage, affecting the overall perfor-
mance of the device.
The MAX9756/MAX9757/MAX9758 feature an audible
alert beep input (BEEP) that accepts a mono system
alert signal and mixes it into the stereo audio path.
When the amplitude of V
the frequency of the beep signal is greater than 300Hz,
the beep signal is mixed into the active audio path
(speaker or headphone). If the signal at V
< 300mV
into the audio path. The amplitude of the BEEP signal at
the device output is roughly the amplitude V
the gain of the selected signal path.
The input resistor (R
amplifier, and thus the amplitude of V
based on:
The total BEEP gain is given by:
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Figure 12. Beep Input
20
______________________________________________________________________________________
P-P
or < 300Hz, the BEEP signal is not mixed
R
SOURCE 1
SOURCE 2
SOURCE 3
B
≤
B
) sets the gain of the BEEP input
V
IN BEEP
0.47µF
0.47µF
0.47µF
BEEP
(
V
BEEP
)
exceeds 300mV
47kΩ
47kΩ
47kΩ
R
R
R
× 47 Ω
B
B
B
k
BEEP
BEEP Input
BEEP
. Choose R
BEEP
BEEP
P-P
is either
BIAS
BIAS
times
and
B
47kΩ
where 47kΩ is the value of the BEEP amplifier feedback
resistor, V
is the BEEP input amplitude, and V
BEEP output signal. A
listed in Table 5. Note that V
300mV
an attenuator, if the original alert signal amplitude is too
large, or to gain up the alert signal if it is below
300mV
the value of the coupling capacitor as described in the
Input Filtering section. Multiple beep inputs can be
summed
Table 5. BEEP Output Gain
*All output gains are for V
HEADPHONE *
(0.3V
(300Hz THRESHOLD)
(V/V)
1.78
1.78
1.78
1.78
FREQUENCY
1.5
1.5
1.5
1.5
P-P
DETECTOR
DETECTOR
P-P
P-P
WINDOW
V
BEEP
THRESHOLD)
(Figure 12).
A
V
. The BEEP amplifier can be set up as either
. AC-couple the alert signal to BEEP. Choose
BEEP
V(BEEPOUT)
OUT BEEP
V
IN BEEP
(
(
is the BEEP amplifier output, V
SPEAKER*
)
)
(V/V)
15.8
18.8
8.4
9.4
V(BEEPOUT
10
10
20
20
=
VOL
⎛
⎜
⎝
47 Ω
SPEAKER/HEADPHONE
R
= GND.
AMPLIFIER INPUTS
MAX9758
MAX9756/
MAX9757/
k
B
BEEP
+
GAIN3
) is given by the values
A
0
0
0
0
1
1
1
1
V BEEPOUT
OUT(BEEP)
must be higher than
(
GAIN2
0
0
1
1
0
0
1
1
)
is the total
⎞
⎟
⎠
IN(BEEP)
GAIN1
0
1
0
1
0
1
0
1