Datasheet
data (see Figure 5). The MAX9723 pulls down SDA dur-
ing the master-generated 9th clock pulse. The SDA line
must remain stable and low during the high period of the
acknowledge clock pulse. Monitoring ACK allows for detec-
tion of unsuccessful data transfers. An unsuccessful data
transfer occurs if a receiving device is busy or if a system
fault has occurred. In the event of an unsuccessful data
transfer, the bus master may reattempt communication.
Write Data Format
A write to the MAX9723 includes transmission of a START
condition, the slave address with the R/W bit reset to 0
(see Table 1), one byte of data to configure the command
register, and a STOP condition. Figure 6 illustrates the
proper format for one frame.
The MAX9723 only accepts write data, but it acknowl-
edges the receipt of its address byte with the R/W bit set
high. The MAX9723 does not write to the SDA bus in the
event that the R/W bit is set high. Subsequently, the mas-
ter reads all 1’s from the MAX9723. Always reset the R/W
bit to 0 to avoid this situation.
Command Register
The MAX9723 has one command register that is used to
enable/disable shutdown, enable/disable BassMax, and
set the maximum gain and volume. Table 2 describes the
function of the bits contained in the command register.
Reset B7 to 0 to shut down the MAX9723. The MAX9723
wakes up from shutdown when B7 is set to 1 provided
SHDN is high. SHDN must be high and B7 must be set
to 1 for the MAX9723 to operate normally (see Table 3).
Set B6 to 1 to enable BassMax (see Table 4). The output
signal’s low-frequency response will be boosted accord-
ing to the external components connected between OUT_
and BB_. See the BassMax Gain-Setting Components
section in the Applications Information section for details
on choosing the external components.
Figure 4. START, STOP, and REPEATED START Conditions Figure 5. Acknowledge
Table 1. MAX9723 Address Map
Table 2. MAX9723 Command Register
Table 3. Shutdown Control, SHDN = 1
Table 4. BassMax Control
PART
MAX9723 SLAVE ADDRESS
A6 A5 A4 A3 A2 A1 A0 R/W
MAX9723A 1 0 0 1 1 0 0 0
MAX9723B 1 0 0 1 1 0 1 0
MAX9723C 1 0 0 1 1 0 0 0
MAX9723D 1 0 0 1 1 0 1 0
B7 B6 B5 B4 B3 B2 B1 B0
SHUTDOWN
BassMax
ENABLE
MAXIMUM
GAIN
VOLUME
MODE B7
MAX9723 Disabled 0
MAX9723 Enabled 1
MODE B6
BassMax Disabled 0
BassMax Enabled 1
SCL
SDA
S Sr P
1
SCL
START
CONDITION
SDA
2 8 9
CLOCK PULSE FOR
ACKNOWLEDGMENT
ACKNOWLEDGE
NOT ACKNOWLEDGE
MAX9723 Stereo DirectDrive Headphone Amplier
with BassMax, Volume Control, and I
2
C
www.maximintegrated.com
Maxim Integrated
│
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