MAX9765ETJ MAXIM [Maxim Integrated Products], MAX9765ETJ Datasheet - Page 22

• Manufacturer Part Number: MAX9765ETJ
• Description: 750mW Audio Amplifiers with Headphone Amp, Microphone Preamp, and Input Mux
• Manufacturer: MAXIM [Maxim Integrated Products]

750mW Audio Amplifiers with Headphone Amp,
Microphone Preamp, and Input Mux
Table 6. Microphone Gain Setting
*Default state.
The MAX9765/MAX9766 are compatible with existing I
systems. SCL and SDA are high-impedance inputs; SDA
has an open drain that pulls the data line low during the
ninth clock pulse. The communication protocol supports
the standard I
address is ignored. The MAX9765/MAX9766 addresses
are compatible with the 7-bit I
only. No 10-bit formats are supported.
The MAX9765/MAX9766/MAX9767 feature speaker
amplifiers designed to drive a load differentially, a con-
figuration referred to as bridge-tied load (BTL). The BTL
configuration (Figure 8) offers advantages over the sin-
gle-ended configuration, where one side of the load is
connected to ground. Driving the load differentially
doubles the output voltage compared to a single-
ended amplifier under similar conditions. Thus, the
devices’ differential gain is twice the closed-loop gain
of the input amplifier. The effective gain is given by:
Substituting 2 x V
ing equations yields four times the output power due to
doubling of the output voltage:
22
______________________________________________________________________________________
MG2
0*
0
0
0
1
1
1
1
2
C 8-bit communications. The general call
Applications Information
OUT(P-P)
A
MG1
0*
0
1
1
0
0
1
1
VD
= ×
2
for V
R
R
IN
F
2
OUT(P-P)
C addressing protocol
MG0
0*
1
0
1
0
1
0
1
I
BTL Amplifiers
2
C Compatibility
into the follow-
DIFF GAIN (dB)
MAX9765
2
C
14
19
24
29
34
39
4
9
Since the outputs are differential, there is no net DC
voltage across the load. This eliminates the need for
DC-blocking capacitors required for single-ended
amplifiers. These capacitors can be large, expensive,
consume board space, and degrade low-frequency
performance.
The MAX9765/MAX9766 can be configured as single-
ended headphone amplifiers through software or by
sensing the presence of a headphone plug (HPS). In
headphone mode, the inverting output of the BTL
amplifier is disabled, muting the speaker. The gain is
1/2 that of the device in speaker mode, and the output
power is reduced by a factor of 4.
In headphone mode, the load must be capacitively
coupled to the device, blocking the DC bias voltage
from the load (see the Typical Application Circuit and
the Output-Coupling Capacitor section).
The MAX9765/MAX9766/MAX9767 feature a low-noise,
high CMRR, differential input microphone amplifier. The
differential input structure is almost essential in noisy
digital systems where amplification of low-amplitude
analog signals is necessary such as notebooks and
PDAs. When properly employed, the differential input
architecture offers the following advantages:
Single-Ended Headphone Amplifier
DIFF GAIN (dB)
MAX9766
P
V
OUT
RMS
10
15
20
25
30
35
40
45
Differential Microphone Amplifier
=
=
V
V
RMS
OUT P P
R
Microphone Amplifiers
2 2
L
(
2
−
)
SINGLE-ENDED GAIN
(dB)
10
15
20
25
29
34
36
40