19-3556; Rev 5; 5/07
IT
TION K
VALUA
E
BLE
AVAILA
2-Wire Interfaced Low-EMI Key Switch
and Sounder Controllers
General Description
Features
♦
400kbps, 5.5V-Tolerant 2-Wire Serial Interface
♦
2.4V to 3.6V Operation
♦
Monitor Up to 64 Keys (MAX7349),
40 Keys (MAX7348), or 24 Keys (MAX7347)
♦
FIFO Queues Up to 8 Debounced Key Events
♦
Key Debounce Time User Configurable from 9ms
to 40ms
♦
Key Autorepeat Rate and Delay User Configurable
♦
Low-EMI Design Uses Static Matrix Monitoring
♦
Hardware Interrupt on Each Debounced Event or
FIFO Level, or at End of Definable Time Period
♦
Up to Six Open-Drain Logic Outputs Available
Capable of Driving LEDs
♦
Sounder Output Generates Automatic Key Clicks
♦
14 Programmable Musical Sounder Frequencies
♦
Continuous or Programmable Sounder Duration
♦
Easy Automatic Single-Tone and Dual-Tone Alarm
Sound Generation
♦
Four I
2
C Address Choices
♦
Selectable 2-Wire Serial Bus Timeout
♦
Under 10µA Shutdown Current
MAX7347/MAX7348/MAX7349
The MAX7347/MAX7348/MAX7349 I
2
C interfaced periph-
erals provide microprocessors with management of up to
64 key switches. Key inputs are monitored statically, not
dynamically scanned, to ensure low-EMI operation. The
MAX7347 can monitor up to 24 switches, the MAX7348
can monitor up to 40 switches, and the MAX7349 can
monitor up to 64 switches. The switches can be metallic
or resistive (carbon) up to 1kΩ.
The key controller debounces and maintains a FIFO of
key-press events (including autorepeat, if enabled). An
interrupt (INT) output can be configured to alert key
presses either as they occur, or at maximum rate.
The MAX7348/MAX7349 feature a tone generator to
generate automatic key-click sounds or alarm tones
under processor control.
The sounder frequencies cover the 5th musical octave
(523.25Hz to 987.77Hz), plus seven other musical
notes up to 2637Hz. The output can also be pro-
grammed to be high or low for the sound duration to
operate an electronic sounder, relay, or lamp.
The MAX7347 is offered in 16-pin QSOP and TQFN
packages. The MAX7348 is offered in a 20-pin QSOP
package. The MAX7349 is available in 24-pin QSOP and
TQFN packages. The MAX7347/MAX7348/MAX7349
operate over the -40°C to +125°C temperature range.
Applications
Medical Instruments
Instrumentation Panels
Security and Access
Industrial Controls
Pin Configurations appear at end of data sheet.
Ordering Information
PART
MAX7347AEE+
MAX7347ATE+
MAX7348AEP+
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-
PACKAGE
16 QSOP
16 TQFN-EP*
20 QSOP
24 QSOP
24 TQFN-EP*
PKG
CODE
E16-4
T1644-4
E20-1
E24-1
T2444-4
Typical Application Circuit
INPUT
2.4V TO 3.6V
V+
MAX7349
COL_
8
SWITCH
ARRAY, UP
TO 64
SWITCHES
MAX7349AEG+
MAX7349ATG+
8
ROW_
SCL
SDA
ALERT
INT
AD0
GND
SOUNDER
+Denotes
lead-free package.
*EP
= Exposed paddle.
PIEZO
TRANSDUCER
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
2-Wire Interfaced Low-EMI Key Switch
and Sounder Controllers
MAX7347/MAX7348/MAX7349
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
V+ ............................................................................-0.3V to +4V
COL2/PORT2–COL7/PORT7 ....................................-0.3V to +4V
SDA, SCL, AD0, ALERT,
INT
....................................-0.3V to +6V
All Other Pins................................................-0.3V to (V+ + 0.3V)
DC Current on COL2/PORT2–COL7/PORT7 ......................25mA
DC Current on SOUNDER ................................................±25mA
GND Current .......................................................................80mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........666mW
16-Pin TQFN (derate 16.9mW/°C above +70°C).......1349.1mW
20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW
24-Pin QSOP (derate 9.5mW/°C above +70°C)...........761mW
24-Pin TQFN (derate 20.8mW/°C above +70°C).......1666.7mW
Operating Temperature Range (T
MIN
to T
MAX
) ...-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V+ = 2.4V to 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V+ = 3.3V, T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Operating Supply Voltage
Operating Supply Current
Shutdown Supply Current
SOUNDER Output High Voltage
SOUNDER Output Low Voltage
SOUNDER Frequency Accuracy
Key-Switch Source Current
Key-Switch Source Voltage
Key-Switch Resistance
Startup Time from Shutdown
Output Low Voltage
COL2/PORT2 to COL7/PORT7,
INT
Output
Input Leakage Current Alert
Input High Voltage ALERT
Input Low Voltage ALERT
Serial Bus Timeout
Input High Voltage
SDA, SCL, AD0
Input Low Voltage
SDA, SCL, AD0
Input Leakage Current
SDA, SCL, AD0
V
IH
V
IL
t
OUT
V
IH
V
IL
Input voltage
≤
V+
Input voltage
>
V+
-1
-5
With bus timeout enabled
20
2.2
0.6
+1
+5
I
KEY
V
KEY
R
KEY
t
START
V
OLPORT
I
SINK
= 10mA
Input voltage
≤
V+
Input voltage
>
V+
-1
-5
2.2
0.8
68
(Note 3)
57
SYMBOL
V+
I+
I
SH
V
OHBUZ
V
OLBUZ
I
SOURCE
= 10mA
I
SINK
= 10mA
T
A
= +25°C, V+ = 3.3V
1.2
28
0.35
40
0.65
1
200
0.15
+1
+5
V+ -
0.45
0.15
All key switches open
CONDITIONS
MIN
2.4
75
6.44
TYP
MAX
3.6
100
10
UNITS
V
µA
µA
V
V
%
µA
V
kΩ
µs
V
µA
V
V
ms
V
V
µA
SERIAL-INTERFACE SPECIFICATIONS
2
_______________________________________________________________________________________
2-Wire Interfaced Low-EMI Key Switch
and Sounder Controllers
I
2
C TIMING CHARACTERISTICS
(V+ = 2.4V to 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V+ = 3.3V, T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Input Capacitance
(SCL, SDA, AD0)
SCL Serial Clock Frequency
Bus Free Time Between a STOP
and a START Condition
Hold Time (Repeated) START
Condition
Repeated START Condition
Setup Time
STOP Condition Setup Time
Data Hold Time
Data Setup Time
SCL Clock Low Period
SCL Clock High Period
Rise Time of Both SDA and SCL
Signals, Receiving
Fall Time of Both SDA and SCL
Signals, Receiving
Fall Time of SDA Transmitting
Pulse Width of Spike Suppressed
Capacitive Load for Each Bus
Line
SYMBOL
C
IN
f
SCL
t
BUF
t
HD, STA
t
SU, STA
t
SU, STO
t
HD, DAT
t
SU, DAT
t
LOW
t
HIGH
t
R
t
F
t
F.TX
t
SP
C
b
(Notes 3, 4)
(Notes 3, 4)
(Notes 3, 6)
(Notes 3, 7)
(Note 3)
(Note 5)
100
1.3
0.7
20 +
0.1C
b
20 +
0.1C
b
20 +
0.1C
b
300
300
250
50
400
(Notes 3, 4)
With bus timeout enabled
With bus timeout disabled
0.05
0
1.3
0.6
0.6
0.6
0.9
CONDITIONS
MIN
TYP
MAX
10
400
400
UNITS
pF
kHz
µs
µs
µs
µs
µs
ns
µs
µs
ns
ns
ns
ns
pF
MAX7347/MAX7348/MAX7349
All parameters are tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
All digital inputs at V+ or GND.
Guaranteed by design.
C
b
= total capacitance of one bus line in pF. t
R
and t
F
measured between 0.8V and 2.1V.
A master device must provide a hold time of at least 300ns for the SDA signal (referred to V
IL
of the SCL signal) to bridge
the undefined region of SCL’s falling edge.
Note 6:
I
SINK
≤
6mA. C
b
= total capacitance of one bus line in pF. t
R
and t
F
measured between 0.8V and 2.1V.
Note 7:
Input filters on the SDA, SCL, and AD0 inputs suppress noise spikes less than 50ns.
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
_______________________________________________________________________________________
3
2-Wire Interfaced Low-EMI Key Switch
and Sounder Controllers
MAX7347/MAX7348/MAX7349
Typical Operating Characteristics
(V+ = 3.3V, T
A
= +25°C, unless otherwise noted. Supply range for V+ is 2.4V to 3.6V. Temperature range is -40°C to +125°C.)
GPO OUTPUT LOW VOLTAGE
vs. SINK CURRENT
MAX7347 toc01
GPO OUTPUT LOW VOLTAGE
vs. SINK CURRENT
MAX7347 toc02
GPO OUTPUT LOW VOLTAGE
vs. SINK CURRENT
V+ = 3.6V
MAX7347 toc03
300
250
200
V
OL
(mV)
150
100
50
0
0
V+ = 2.4V
300
250
200
V
OL
(mV)
V+ = 3V
300
250
200
V
OL
(V)
T
A
= +125°C
T
A
= +125°C
150
100
T
A
= -40°C
50
0
T
A
= +25°C
T
A
= +125°C
150
100
50
0
T
A
= -40°C
T
A
= +25°C
T
A
= -40°C
T
A
= +25°C
5
10
15
20
25
0
5
10
15
20
25
0
5
10
15
20
25
I
SINK
(mA)
I
SINK
(mA)
I
SINK
(mA)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX7347 toc04
KEY-SWITCH SOURCE CURRENT
vs. SUPPLY VOLTAGE
MAX7347 toc05
SOUNDER FREQUENCY
vs. SUPPLY VOLTAGE
SOUNDER FREQUENCY
CONFIGURED FOR 880Hz
MAX7347 toc06
90
85
80
SUPPLY CURRENT (μA)
75
70
65
60
55
50
45
40
2.4
2.6
2.8
3.0
3.2
3.4
T
A
= -40°C
T
A
= +125°C
T
A
= +25°C
30
KEY-SWITCH SOURCE CURRENT (μA)
29
COL0 = GND
T
A
= -40°C
886
884
SOUNDER FREQUENCY (Hz)
882
880
878
876
874
28
27
T
A
= +25°C
26
25
24
T
A
= +125°C
T
A
= -40°C
T
A
= +25°C
T
A
= +125°C
3.6
2.4
2.6
2.8
3.0
3.2
3.4
3.6
2.4
2.7
3.0
3.3
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SOUNDER OUTPUT
MAX7347 toc07
OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
MAX7347 toc08
OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX7347 toc09
65
OSCILLATOR FREQUENCY (kHz)
65
OSCILLATOR FREQUENCY (kHz)
64
64
3V
V
SOUNDER
1V/div
0V
63
63
62
62
61
61
60
200μs/div
2.4
2.7
3.0
3.3
3.6
SUPPLY VOLTAGE (V)
60
-40
10
60
110
TEMPERATURE (°C)
4
_______________________________________________________________________________________
2-Wire Interfaced Low-EMI Key Switch
and Sounder Controllers
Pin Description
PIN
MAX7347 MAX7347
MAX7349 MAX7349
MAX7348
(QSOP)
(TQFN)
(QSOP)
(TQFN)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
—
—
—
15
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
—
—
—
1
2
3
4
7
8
9
10
11
12
13
15
17
18
19
20
5
6
14
2
3
4
5
8
9
10
11
14
15
16
18
20
21
22
23
6
7
17
23
24
1
2
5
6
7
8
11
12
13
15
17
18
19
20
3
4
14
NAME
ROW0
ROW1
ROW2
ROW3
ROW4
ROW5
ROW6
ROW7
COL1
COL0
GND
SDA
SCL
INT
V+
FUNCTION
Row Input from Key Matrix. Leave open circuit if unused.
Row Input from Key Matrix. Leave open circuit if unused.
Row Input from Key Matrix. Leave open circuit if unused.
Row Input from Key Matrix. Leave open circuit if unused.
Row Input from Key Matrix. Leave open circuit if unused.
Row Input from Key Matrix. Leave open circuit if unused.
Row Input from Key Matrix. Leave open circuit if unused.
Row Input from Key Matrix. Leave open circuit if unused.
Column Output to Key Matrix
Column Output to Key Matrix
Ground
I2C-Compatible Serial Data I/O
I2C-Compatible Serial Clock Input
Active-Low Interrupt Output. Output is open drain.
Positive Supply Voltage. Bypass V+ to GND with a
0.047µF or higher ceramic capacitor.
MAX7347/MAX7348/MAX7349
COL2/PORT2 Column Output to Key Matrix or GPO
COL3/PORT3 Column Output to Key Matrix or GPO
COL4/PORT4 Column Output to Key Matrix or GPO
SOUNDER
Sounder Driver Output. Typically connect a piezo-ceramic
sounder or other transducer from this output to ground.
Output is push-pull.
Address Input 0. Sets device slave address. Connect to
GND, V+, SDA, or SCL to give four logic combinations.
See Table 3.
—
—
—
—
—
—
—
—
—
—
—
EP
16
—
—
—
—
—
19
1
12
13
24
—
16
22
9
10
21
EP
AD0
COL7/PORT7 Column Output to Key Matrix or GPO
COL6/PORT6 Column Output to Key Matrix or GPO
COL5/PORT5 Column Output to Key Matrix or GPO
ALERT
EP
Alert Input. Connect to GND or V+ if unused.
Exposed Paddle. Internally connected to GND. Connect to
a large ground plane to maximize thermal performance.
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
5
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