MAX7347/MAX7348/MAX7349
2-Wire Interfaced Low-EMI Key Switch
and Sounder Controllers
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5
Detailed Description
The MAX7347/MAX7348/MAX7349 are microprocessor
peripherals that combine a low-noise key-switch inter-
face with a piezo sounder controller. Up to 64 key
switches can be monitored and debounced with optional
autorepeat, and the key events are presented in an
eight-deep FIFO. Key-switch functionality can be traded
to provide up to one (MAX7347), three (MAX7348), or six
(MAX7349) open-drain logic outputs. (Table 1).
The piezo sounder controller generates a variety of
audio tones. Tones are programmable for frequency
and duration, and may be intermittent, two tone, or con-
tinuous. The piezo sounder controller can be config-
ured to deliver an automatic, customizable sound on
every key press to provide a udible key-click feedback.
Interrupt requests can be configured to be issued on
every key-press event, or can be limited to a maximum
rate to prevent overloading the microprocessor with
Pin Description
PIN
MAX7347
(QSOP)
MAX7347
(TQFN)
MAX7348
MAX7349
(QSOP)
MAX7349
(TQFN)
NAME
FUNCTION
1
15
1
2
23
ROW0
Row Input from Key Matrix. Leave open circuit if unused.
2
16
2
3
24
ROW1
Row Input from Key Matrix. Leave open circuit if unused.
3
1
3
4
1
ROW2
Row Input from Key Matrix. Leave open circuit if unused.
4
2
4
5
2
ROW3
Row Input from Key Matrix. Leave open circuit if unused.
5
3
7
8
5
ROW4
Row Input from Key Matrix. Leave open circuit if unused.
6
4
8
9
6
ROW5
Row Input from Key Matrix. Leave open circuit if unused.
7
5
9
10
7
ROW6
Row Input from Key Matrix. Leave open circuit if unused.
8
6
10
11
8
ROW7
Row Input from Key Matrix. Leave open circuit if unused.
9
7
11
14
11
COL2/PORT2 Column Output to Key Matrix or GPO
10
8
12
15
12
COL1
Column Output to Key Matrix
11
9
13
16
13
COL0
Column Output to Key Matrix
12
10
15
18
15
GND
Ground
13
11
17
20
17
SDA
I2C-Compatible Serial Data I/O
14
12
18
21
18
SCL
I2C-Compatible Serial Clock Input
15
13
19
22
19
INT
Active-Low Interrupt Output. Output is open drain.
16
14
20
23
20
V+
Positive Supply Voltage. Bypass V+ to GND with a
0.047F or higher ceramic capacitor.
—
5
6
3
COL3/PORT3 Column Output to Key Matrix or GPO
—
6
7
4
COL4/PORT4 Column Output to Key Matrix or GPO
—
14
17
14
SOUNDER
Sounder Driver Output. Typically connect a piezo-ceramic
sounder or other transducer from this output to ground.
Output is push-pull.
——16
19
16
AD0
Address Input 0. Sets device slave address. Connect to
GND, V+, SDA, or SCL to give four logic combinations.
See Table 3.
—
1
22
COL7/PORT7 Column Output to Key Matrix or GPO
—
12
9
COL6/PORT6 Column Output to Key Matrix or GPO
—
13
10
COL5/PORT5 Column Output to Key Matrix or GPO
—
24
21
ALERT
Alert Input. Connect to GND or V+ if unused.
—EP
—
EP
Exposed Paddle. Internally connected to GND. Connect to
a large ground plane to maximize thermal performance.