19-5950; Rev 1; 3/12
EVALUATION KIT AVAILABLE
MAX7370
8 x 8 Key-Switch Controller and LED Driver/GPIOs
with I
2
C Interface and High Level of ESD Protection
General Description
The MAX7370 I
2
C-interfaced peripheral provides micro-
processors with management of up to 64 key switches,
with optional GPIO and PWM-controlled LED drivers.
The key-switch drivers interface with metallic or resistive
switches with on-resistances up to 5kI. Key inputs are
monitored statically, not dynamically, to ensure low-EMI
operation. The IC features autosleep and autowake
modes to further minimize the power consumption of
the device. The autosleep feature puts the device in a
low-power state (1µA typ) after a timeout period. The
autowake feature configures the device to return to
normal operating mode from sleep upon a keypress.
The key controller debounces and maintains a FIFO
buffer of keypress and release events (including auto-
repeat, if enabled). An interrupt (INT) output can be
configured to alert keypresses, as they occur, or at the
maximum rate.
The same index rows and columns in the device can be
used as a direct logic-level translator.
If the device is not used for key-switch control, all
keyboard pins can be used as GPIOs. Each GPIO can
be programmed to one of the two externally applied
logic voltage levels. Four column ports (COL7–COL4)
can also be configured as LED drivers that feature
constant-current and PWM intensity control. The maximum
constant-current level for each open-drain LED port is
20mA. The intensity of the LED on each open-drain port
can be individually adjusted through a 256-step PWM
control.
The device is offered in a 24-pin (3.5mm x 3.5mm) TQFN
package with an exposed pad, and small 25-bump
(2.159mm x 2.159mm) wafer-level package (WLP) for
cell phones, pocket PCs, and other portable consumer
electronic applications.
The device operates over the -40°C to +85°C extended
temperature range.
Features
S
Monitors Up to 64 Keys
S
Integrated High-ESD Protection
±8kV IEC 61000-4-2 Contact Discharge
±15kV IEC 61000-4-2 Air-Gap Discharge
S
Keyscan Uses Static Matrix Monitoring for
Low-EMI Operation
S
Four LED Driver Pins on COL7–COL4
S
5V Tolerant, Open-Drain I/O Ports Capable of
Constant-Current LED Drive
S
256-Step PWM Individual LED Intensity-Control
Accuracy
S
Individual LED Blink Rates and Common LED
Fade In/Out Rates from 256ms to 4096ms
S
FIFO Queues Up to 16 Debounced Key Events
S
User-Configurable Keypress and Release
Debounce Time (2ms to 32ms)
S
Key-Switch Interrupt (INT) on Each Debounced
Event/FIFO Level, or End-of-Definable Time Period
S
1.62V to 3.6V Operating Supply Voltage
S
Individually Programmable GPIOs to Two Logic
Levels
S
8-Channel Individual Programmable Level
Translators
S
Provides Optional GPIOs on all ROW½ and COL½
Pins
S
Supports Hot Insertion
S
400kbps, 5.5V Tolerant I
2
C Serial Interface with
Selectable Bus Timeout
Ordering Information
appears at end of data sheet.
Typical Operating Circuit
+1.8V
V
CC
+2.6V
V
LA
COL4
COL5
COL6
COL7
ROW[0:7]
GND
COL[0:3]
8
4
32 KEYS
+5V
Applications
Cell Phones
Notebooks
PDAs
Handheld Games
Portable Consumer Electronics
For related parts and recommended products to use with this part,
refer to
www.maxim-ic.com/MAX7370.related.
MCU
INT
SDA
SCL
AD0
MAX7370
I/O
I/O
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX7370
8 x 8 Key-Switch Controller and LED Driver/GPIOs
with I
2
C Interface and High Level of ESD Protection
ABSOLUTE MAXIMUM RATINGS
V
CC
, V
LA
to GND ....................................................-0.3V to +4V
COL3–COL0, ROW7–ROW0 to GND ....... -0.3V to (V
CC
+ 0.3V)
COL7–COL4 to GND ...............................................-0.3V to +6V
SDA, SCL, AD0,
INT
to GND ..................................-0.3V to +6V
V
LA
to V
CC
...........................................................-0.3V to +2.3V
DC Current on COL7–COL4 to GND .................................25mA
DC Current on COL3–COL0, ROW7–ROW0 to GND...........7mA
V
CC
, V
LA
, GND Current .....................................................80mA
DC Current V
CC
, V
LA
to COL3–COL0, ROW7–ROW0 .........5mA
Continuous Power Dissipation (T
A
= +70°C)
24-Pin TQFN (derate 15.4mW/°C above +70°C) ......1229mW
25-Bump WLP (derate 19.2mW/°C above +70°C)......850mW
Operating Temperature Range .......................... -40°C to +85°C
Junction Temperature .....................................................+150°C
Storage Temperature Range............................ -65°C to +150°C
Lead Temperature (TQFN) (soldering, 10s) ...................+300°C
Soldering Temperature (reflow) ......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion 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.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
24 TQFN
Junction-to-Ambient Thermal Resistance (B
JA
) .........65.1°C/W
Junction-to-Case Thermal Resistance (B
JC
) ................5.4°C/W
25 WLP
Junction-to-Ambient Thermal Resistance (B
JA
) ...........52°C/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(V
CC
= 1.62V to 3.6V, T
A
= -40NC to +85NC, unless otherwise noted. Typical values are at V
CC
= 3.3V, T
A
= +25NC.) (Notes 2, 3)
PARAMETER
Operating Supply Voltage
Second Logic Supply
SYMBOL
V
CC
V
LA
I
CC
All key switches open, oscillator
running
N keys pressed
Sleep-Mode Supply Current
POR Threshold
KEY-SWITCH SPECIFICATIONS
Key-Switch Source Current
Key-Switch Source Voltage
Key-Switch Resistance
Startup Time from Sleep
GPIO SPECIFICATIONS
External Supply Voltage
COL7–COL4 (LED Drivers)
LED Port-to-Port Sink Current Variation
V
LED
V
CC
= 3.3V, V
OL
= 1V, T
A
= +25NC,
10mA output mode
Q1.5
5
Q2.4
V
%
I
KEY
V
KEY
R
KEY
t
START
(Note 4)
2
28
0.45
40
0.5
5
2.7
FA
V
kI
ms
I
SL
V
POR
Not using GPO or LED configuration
CONDITIONS
MIN
1.62
V
CC
TYP
3.3
3.3
50
50 + 28
O
N
1.8
1.2
3
FA
V
MAX
3.6
3.6
65
FA
UNITS
V
V
Operating Supply Current
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Maxim Integrated Products
2
MAX7370
8 x 8 Key-Switch Controller and LED Driver/GPIOs
with I
2
C Interface and High Level of ESD Protection
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 1.62V to 3.6V, T
A
= -40NC to +85NC, unless otherwise noted. Typical values are at V
CC
= 3.3V, T
A
= +25NC.) (Notes 2, 3)
PARAMETER
10mA Port Sink Current
COL7–COL4
SYMBOL
V
OL
= 1V
I
OL
V
OL
= 0.5V
V
OL
= 1V
I
OL
V
OL
= 0.5V
V
IH
V
IL
I
LEAKAGE
I
LEAKAGE
C
IN
N keys pressed simultaneously
V
OL
V
CC
= 1.62V and I
SINK
= 2.5mA
V
CC
= 1.62V and I
SINK
= 5mA
V
CC
= 1.62V and I
SOURCE
= 2.5mA
V
OH
V
CC
= 1.62V and I
SOURCE
= 5mA
V
OL
f
PWM
V
IH
V
IL
I
LEAKAGE
V
OL
C
IN
Input voltage = 5.5V or V
GND
I
SINK
= 6mA
(Notes 4, 5)
-1
I
SINK
= 6mA
Derived from oscillator clock
500
V
CC
-
120
V
CC
-
250
CONDITIONS
T
A
= +25NC
V
CC
= 3.3V
V
CC
= 3.6V,
T
A
= +25NC
T
A
= +25NC
V
CC
= 3.3V
V
CC
= 3.6V,
T
A
= +25NC
0.7
O
V
S
0.3
O
V
S
-2
-1
20
500
50
80
V
CC
-
40
V
CC
-
70
0.6
100
250
+2
+1
18.13
18.47
20
19.05
V
V
FA
FA
pF
pF
mV
MIN
8.6
9.04
10
9.5
21.52
21.34
mA
TYP
MAX
11.4
10.96
mA
UNITS
20mA Port Sink Current
COL7–COL4
Input High Voltage
COL_, ROW_
Input Low Voltage
COL_, ROW_
Input Leakage Current
COL3–COL0, ROW_
Input Leakage Current
COL7–COL4
Input Capacitance
COL_, ROW_
Maximum Allowable Load Capacitance
for Keyscan Function
Output Low Voltage
COL_, ROW_
Output High Voltage
COL3–COL0, ROW_
Output Logic-Low Voltage
(INT)
PWM Frequency
SERIAL-INTERFACE SPECIFICATIONS
Input High Voltage
SDA, SCL, AD0
Input Low Voltage
SDA, SCL, AD0
Input Leakage Current
SDA, SCL, AD0
Output Logic-Low Voltage
SDA
Input Capacitance
SDA, SCL, AD0
V
S
= V
CC
or V
LA
depending on
reference logic level setting
Input voltage = V
CC
or V
GND
Input voltage = 5V
mV
V
Hz
0.7
O
V
CC
0.3
O
V
CC
+1
0.6
10
V
V
FA
V
pF
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Maxim Integrated Products
3
MAX7370
8 x 8 Key-Switch Controller and LED Driver/GPIOs
with I
2
C Interface and High Level of ESD Protection
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 1.62V to 3.6V, T
A
= -40NC to +85NC, unless otherwise noted. Typical values are at V
CC
= 3.3V, T
A
= +25NC.) (Notes 2, 3)
PARAMETER
I
2
C
TIMING SPECIFICATIONS
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
t
TIMEOUT
IEC 61000-4-2 Air-Gap Discharge
ROW7–ROW0, COL7–COL0
IEC 61000-4-2 Contact Discharge
All Other Pins
Note
Note
Note
Note
Note
2:
3:
4:
5:
6:
Human Body Model
Q8
Q2.5
kV
(Notes 4, 5)
(Notes 4, 5)
(Notes 4, 7)
(Notes 4, 8)
(Note 4)
14
19
(Note 6)
100
1.3
0.7
20 +
0.1C
B
20 +
0.1C
B
20 +
0.1C
B
300
300
250
50
400
27
Bus timeout enabled
Bus timeout disabled
0.05
0
1.3
0.6
0.6
0.6
0.9
400
400
kHz
Fs
Fs
Fs
Fs
Fs
ns
Fs
Fs
ns
ns
ns
ns
pF
ms
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SCL Serial-Clock Frequency
Bus Free Time Between a STOP and
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 Signal, Transmitting
Pulse Width of Spike Suppressed
Capacitive Load for Each Bus Line
Bus Time Out
ESD PROTECTION
Q15
kV
All parameters are tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
All digital inputs at V
CC
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 7:
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 8:
Input filters on the SDA, SCL, and AD0 inputs suppress noise spikes less than 50ns.
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Maxim Integrated Products
4
MAX7370
8 x 8 Key-Switch Controller and LED Driver/GPIOs
with I
2
C Interface and High Level of ESD Protection
Typical Operating Characteristics
(V
CC
= 2.5V, V
LA
= 2.5V, T
A
= +25NC, unless otherwise noted.)
GPO OUTPUT LOW VOLTAGE
vs. SINK CURRENT (COL7–COL4)
MAX7370 toc01
GPO OUTPUT LOW VOLTAGE
vs. SINK CURRENT (COL7–COL4)
MAX7370 toc02
GPO OUTPUT LOW VOLTAGE
vs. SINK CURRENT (COL7–COL4)
V
CC
= 3.6V
T
A
= +85°C
80
60
40
20
0
T
A
= -40°C
2
4
6 8 10 12 14 16 18 20
SINK CURRENT (mA)
T
A
= +25°C
MAX7370 toc03
120
GPO OUTPUT LOW VOLTAGE (mV)
100
80
60
40
20
0
0
V
CC
= 2.4V
T
A
= +85°C
120
GPO OUTPUT LOW VOLTAGE (mV)
100
80
60
40
20
0
V
CC
= 3.0V
T
A
= +85°C
120
GPO OUTPUT LOW VOLTAGE (mV)
100
T
A
= +25°C
T
A
= +25°C
T
A
= -40°C
T
A
= -40°C
2
4
6 8 10 12 14 16 18 20
SINK CURRENT (mA)
0
2
4
6 8 10 12 14 16 18 20
SINK CURRENT (mA)
0
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX7370 toc04
KEY-SWITCH SOURCE CURRENT
vs. SUPPLY VOLTAGE
V
COL0
= 0V
SLEEP-MODE SUPPLY CURRENT (µA)
KEY-SWITCH SOURCE CURRENT (µA)
T
A
= +85°C
MAX7370 toc05
SLEEP-MODE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
T
A
= -40°C
1.6
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
AUTOSLEEP = OFF
T
A
= +85°C
55
SUPPLY CURRENT (µA)
50
45
40
26.5
26.0
25.5
T
A
= +25°C
25.0
24.5
T
A
= -40°C
24.0
T
A
= +85°C
T
A
= +25°C
T
A
= +25°C
T
A
= -40°C
35
30
1.6
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
1.6
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
CONSTANT-CURRENT GPIO OUTPUT SINK CURRENT (mA)
CONSTANT-CURRENT GPIO OUTPUT SINK CURRENT (mA)
MAX7370 toc07
MAX7370 toc08
V
CC
= 2.4V
20
T
A
= +85°C
V
CC
= 3.0V
20
T
A
= +85°C
V
CC
= 3.6V
20
T
A
= +85°C
T
A
= +25°C
15
10
5
0
0
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT VOLTAGE (V)
T
A
= +25°C
15
10
5
0
0
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT VOLTAGE (V)
T
A
= +25°C
15
10
5
0
0
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT VOLTAGE (V)
T
A
= -40°C
T
A
= -40°C
T
A
= -40°C
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Maxim Integrated Products
5
MAX7370 toc09
25
25
CONSTANT-CURRENT GPIO OUTPUT SINK CURRENT (mA)
CONSTANT-CURRENT GPIO OUTPUT SINK
CURRENT vs. OUTPUT VOLTAGE (COL7–COL4)
CONSTANT-CURRENT GPIO OUTPUT SINK
CURRENT vs. OUTPUT VOLTAGE (COL7–COL4)
CONSTANT-CURRENT GPIO OUTPUT SINK
CURRENT vs. OUTPUT VOLTAGE (COL7–COL4)
25
MAX7370 toc06
60
27.0
1.8
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