MAX7359
2-Wire Interfaced Low-EMI
Key Switch Controller/GPO
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Detailed Description
The MAX7359 is a microprocessor peripheral low-noise
key-switch controller that monitors up to 64 key switches
with optional autorepeat, and key events are presented
in a 16-byte FIFO. Key-switch functionality can be traded
to provide up to six open-drain logic outputs.
The MAX7359 features an automatic sleep mode and
automatic wakeup that further reduce supply current con-
sumption. The MAX7359 can be configured to enter sleep
mode after a programmable time following a key event.
The FIFO content is maintained during sleep mode and
can be read in sleep mode. The MAX7359 does not enter
autosleep when a key is held down. The autowake feature
takes the MAX7359 out of sleep mode following a key-
press event. Autosleep and autowake can be disabled.
Interrupt requests can be configured to be issued on a
programmable number of FIFO entries, or can be set
to a period of time to prevent overloading the micro-
processor with too many interrupts. The key-switch sta-
tus can be checked at any time by reading the
key-switch FIFO. A 1-byte read access returns both the
next key-event in the FIFO (if there is one) and the
FIFO status, so it is easy to operate the MAX7359 by
polling. If the INT pin is not required, it can be config-
ured as an open-drain general-purpose output (GPO)
capable of driving an LED.
If the application requires fewer keys to be scanned, up
to six of the key-switch outputs can be configured as
open-drain GPOs capable of driving LEDs. For each
key-switch output used as a GPO, the number of key
switches that can be scanned is reduced by eight.
Pin Description
PIN
TQFN WLP
NAME FUNCTION
1A1
ROW2 Row Input from Key Matrix. Leave ROW2 unconnected or connect to GND if unused.
2A2
ROW3 Row Input from Key Matrix. Leave ROW3 unconnected or connect to GND if unused.
3A3
COL3/PORT3 Column Output to Key Matrix or GPO. Leave COL3/PORT3 unconnected if unused.
4B3
COL4/PORT4 Column Output to Key Matrix or GPO. Leave COL4/PORT4 unconnected if unused.
5A4
ROW4 Row Input from Key Matrix. Leave ROW4 unconnected or connect to GND if unused.
6A5
ROW5 Row Input from Key Matrix. Leave ROW5 unconnected or connect to GND if unused.
7B5
ROW6 Row Input from Key Matrix. Leave ROW6 unconnected or connect to GND if unused.
8B4
ROW7 Row Input from Key Matrix. Leave ROW7 unconnected or connect to GND if unused.
9C5
COL6/PORT6 Column Output to Key Matrix or GPO. Leave COL6/PORT6 unconnected if unused.
10 C4
COL5/PORT5 Column Output to Key Matrix or GPO. Leave COL5/PORT5 unconnected if unused.
11 D5
COL2/PORT2 Column Output to Key Matrix or GPO. Leave COL2/PORT2 unconnected if unused.
12 E5
COL1 Column Output to Key Matrix. Leave COL1 unconnected if unused.
13 E4
COL0 Column Output to Key Matrix. Leave COL0 unconnected if unused.
14 D4
I.C. Internally Connected. Connect to GND for normal operation.
15 D3
GND Ground
16 E3
AD0 Adddress Input. ADO selects up to four device slave addresses (Table 10).
17 E2
SDA I
2
C-Compatible, Serial-Data I/O
18 D2
SCL I
2
C-Compatible, Serial-Clock Input
19 E1
INT Active-Low Interrupt Output. INT is open drain.
20 D1
V
CC
Positive Supply Voltage. Bypass V
CC
to GND with a 0.047µF or higher ceramic capacitor.
21 C2, C3
N.C. No Connection. Not internally connected.
22 C1
COL7/PORT7 Column Output to Key Matrix or GPO. Leave COL7/PORT7 unconnected is unused.
23 B2
ROW0 Row Input from Key Matrix. Leave ROW0 unconnected or connect to GND if unused.
24 B1
ROW1 Row Input from Key Matrix. Leave ROW1 unconnected or connect to GND if unused.
——
EP
Exposed Pad (TQFN only). EP internally is connected to GND. Connect EP to a ground plane
to increase thermal performance.
