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MAX9777/MAX9778
Stereo 3W Audio Power Amplifiers with
Headphone Drive and Input Mux
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17
Read Data Format
In read mode (R/W = 1), the MAX9777 writes the con-
tents of the selected register to the bus. The direction of
the data flow reverses following the address acknowl-
edge by the MAX9777. The master device reads the
contents of all registers, including the read-only status
register. Table 6 shows the status register format.
Interrupt Output (INT)
The MAX9777 includes an interrupt output (INT) that
can indicate to a master device that an event has
occurred. INT is triggered when the state of HPS
changes. During normal operation, INT idles high. If a
headphone is inserted/removed from the jack and that
action is detected by HPS, INT pulls the line low. INT
remains low until a read data operation is executed.
I
2
C Compatibility
The MAX9777 is compatible with existing I
2
C 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
2
C 8-bit communications. The general call
address is ignored. The MAX9777 slave addresses are
compatible with the 7-bit I
2
C addressing protocol only.
*Default
REGISTER ADDRESS 0000 0011
BIT NAME VALUE DESCRIPTION
7 X Don’t Care —
6 X Don’t Care —
5 X Don’t Care —
0* Speaker mode selected
4 SPKR/HP
1
Headphone mode
selected
0* Gain-setting A selected
3 GAINA/B
1 Gain-setting B selected
0*
Automatic headphone
detection enabled
2 HPS_D
1
Automatic headphone
detection disabled
(HPS ignored)
0* Input 1 selected
1 IN1/IN2
1 Input 2 selected
0 X Don’t Care —
Table 5. MAX9777 Control Register Format
REGISTER ADDRESS 0000 0000
BIT NAME VALUE DESCRIPTION
0 Device temperature below thermal limit
7 THRM
1 Device temperature exceeding thermal limit
0 OUTR- current below current limit
6 AMPR-
1 OUTR- current exceeding current limit
0 OUTR+ current below current limit
5 AMPR+
1 OUTR+ current exceeding current limit
0 OUTL- current below current limit
4 AMPL-
1 OUTL- current exceeding current limit
0 OUTL+ current below current limit
3 AMPL+
1 OUTL+ current exceeding current limit
0 Device in speaker mode
2 HPSTS
1 Device in headphone mode
1 X Don’t Care —
0 X Don’t Care —
Table 6. MAX9777 Status Register Format