Maxim MAX7359, MAX7359ETG+ Datasheet

General Description

The MAX7359 I2C interfaced peripheral provides micro­processors with management of up to 64 key switches.
Key codes are generated for each press and release of
a key for easier implementation of multiple key entries.
Key inputs are monitored statically, not dynamically, to
ensure low-EMI operation. The switches can be metallic
or resistive (carbon) with up to 5kΩ of resistance.

The MAX7359 features autosleep and autowake to fur­ther minimize the power consumption of the device.
The autosleep feature puts the device in a low-power
state (1µA typ) after a sleep timeout period. The
autowake feature configures the MAX7359 to return to
normal operating mode from sleep upon a key press.

The key controller debounces and maintains a FIFO of
key-press and release events (including autorepeat, if
enabled). An interrupt (INT) output can be configured to
alert key presses either as they occur, or at maximum rate.

Any of the column drivers (COL2/PORT2–COL7/PORT7)
or the INT, if not used, can function as a general-pur­pose output (GPO).

The MAX7359 is offered in a small 24-pin TQFN (3.5mm x

3.5mm) package for cell phones, pocket PCs, and other
portable consumer electronic applications. The MAX7359
operates over the -40°C to +85°C temperature range.

Applications

Cell Phones

PDAs

Handheld Games

Portable Consumer Electronics

Features

♦ Optional Key Release Detection on All Keys

♦ Monitor Up to 64 Keys

♦ 1.62V to 3.6V Operation

♦ Autosleep and Autowake to Minimize Current

Consumption

♦ Under 1µA Sleep Current

♦ FIFO Queues Up to 16 Debounced Key Events

♦ Key Debounce Time User Configurable from 9ms

to 40ms

♦ Low-EMI Design Uses Static Matrix Monitoring

♦ Hardware Interrupt at the FIFO Level or at the End

of Definable Time Period

♦ Up to Seven Open-Drain Logic Outputs Available

Capable of Driving LEDs

♦ 400kbps, 5.5V-Tolerant, 2-Wire Serial Interface

♦ Selectable 2-Wire, Serial-Bus Timeout

♦ Four I

2

C Address Choices

♦ Small, 24-Pin TQFN Package (3.5mm x 3.5mm)

MAX7359

2-Wire Interfaced Low-EMI

Key Switch Controller/GPO

________________________________________________________________

Maxim Integrated Products

1

Ordering Information

19-0850; Rev 0; 7/07

EVALUATION KIT

AVAILABLE

+

Denotes a lead-free package.

*

EP = Exposed paddle.

MAX7359

V

CC

COL_

GND

8

SCL
SDA

AD0

ROW_

8

SWITCH

ARRAY,

UP TO 64

SWITCHES

INPUT

1.62V TO 3.6V

INT

Typical Application Circuit

Pin Configuration appears at end of data sheet.

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.

PART

MAX7359ETG+

TEMP

RANGE

-40°C to
+85°C

PIN-PACKAGE

24 TQFN-EP*
(3.5mm x 3.5mm)

PKG

CODE

T243A3-1

MAX7359

2-Wire Interfaced Low-EMI
Key Switch Controller/GPO

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

(All voltages referenced to GND.)
V

CC

..........................................................................-0.3V to +4V

COL2/PORT2–COL7/PORT7 ....................................-0.3V to +4V

SDA, SCL, AD0, INT .................................................-0.3V to +6V

All Other Pins..............................................-0.3V to (V

CC

+ 0.3V)

DC Current on COL2/PORT2–COL7/PORT7 ......................25mA

GND Current .......................................................................80mA

Continuous Power Dissipation (T

A

= +70°C)

24-Pin TQFN (derate 15.4mW/°C above +70°C)..........1229mW

Operating Temperature Range (T

MIN

to T

MAX

) .....-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(VCC= 1.62V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= 2.5V, TA= +25°C.) (Notes 1, 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Supply Voltage V

Operating Supply Current I

Sleep-Mode Supply Current I

POR 1.0 1.6 V

POR Hysteresis PORHYST VCC rising 42 mV

Key-Switch Source Current I

Key-Switch Source Voltage V

Key-Switch Resistance R

Startup Time from Shutdown t

Output Low Voltage
COL2/PORT2 to COL7/PORT7

INT Output V

Oscillator Frequency F

SERIAL-INTERFACE SPECIFICATIONS

Serial Bus Timeout t

Input High Voltage
SDA, SCL, AD0

Input Low Voltage
SDA, SCL, AD0

Output Low Voltage SDA V

Input Leakage Current VCC = 0 to 6V -1 +1 µA

CC

All key switches open, oscillator running,

CC

SL

KEY

KEY

KEY

START

V

OLPORTISINK

OLINTISINK

OSC

OUT

V

V

OLPORTISINK

COL2–COL7 configured as key switches

N keys pressed

Operating mode 0.42 0.55 V

(Note 3) 5 kΩ

= 10mA 0.2 V

= 10mA 0.5 V

With bus timeout enabled 10 40 ms

IH

IL

= 10mA 0.4 V

1.62 3.60 V

0.7 x
V

CC

25 60

(25 +

20 x N)

0.6 5 µA

20 35 µA

2000 2400 µs

64 kHz

0.3 x
V

CC

µA

V

V

MAX7359

2-Wire Interfaced Low-EMI

Key Switch Controller/GPO

_______________________________________________________________________________________ 3

I2C TIMING CHARACTERISTICS

(VCC= 1.62V to 3.6V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= 2.5V, TA= +25°C.) (Notes 1, 2) (Figure 2)

Note 1: All parameters are tested at TA= +25°C. Specifications over temperature are guaranteed by design.
Note 2: All digital inputs at V

CC

or GND.

Note 3: Guaranteed by design.
Note 4: C

b

= total capacitance of one bus line in pF. tRand tFmeasured between 0.8V and 2.1V.

Note 5: 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. Cb= total capacitance of one bus line in pF. tRand tFmeasured between 0.8V and 2.1V.

Note 7: Input filters on the SDA, SCL, and AD0 inputs suppress noise spikes less than 50ns.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Input Capacitance
(SCL, SDA, AD0)

SCL Serial-Clock Frequency f

Bus Free Time Between a STOP
and a START Condition

Hold Time (Repeated) START
Condition

Repeated START Condition
Setup Time

STOP Condition Setup Time t

Data Hold Time t

Data Setup Time t

SCL Clock Low Period t

SCL Clock High Period t

Rise Time of Both SDA and SCL
Signals, Receiving

Fall Time of Both SDA and SCL
Signals, Receiving

Fall Time of SDA Transmitting t

Pulse Width of Spike Suppressed t

C ap aci ti ve Load for E ach Bus Li ne C

C

IN

SCL

t

BUF

t

HD, STA

t

SU, STA

SU, STO

HD, DAT

SU, DAT

LOW

HIGH

t

R

t

F

F.TX

SP

b

(Notes 3, 4) 10 pF

Bus timeout disabled 0 400 kHz

1.3 µs

0.6 µs

0.6 µs

0.6 µs

(Note 5) 0.9 µs

100 ns

1.3 µs

0.7 µs

(Notes 3, 4)

(Notes 3, 4)

(Notes 3, 6)

(Notes 3, 7) 50 ns

(Note 3) 400 pF

20 +

0.1C

20 +

0.1C

20 +

0.1C

b

b

b

300 ns

300 ns

250 ns

MAX7359

2-Wire Interfaced Low-EMI
Key Switch Controller/GPO

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= 2.5V, TA= +25°C, unless otherwise noted.)

GPO PORT OUTPUT LOW VOLTAGE

vs. SINK CURRENT

300

VCC = +2.4V

250

200

(mV)

150

OL

V

100

50

0

010155 202530

SUPPLY CURRENT vs. SUPPLY VOLTAGE

40

AUTOSLEEP = OFF

35

30

25

SUPPLY CURRENT (μA)

20

15

1.6 2.42.0 2.8 3.2 3.6

TA = +85°C

SUPPLY VOLTAGE (V)

TA = +85°C

TA = +25°C

I

(mA)

SINK

TA = +25°C

= -40°C

T

A

TA = -40°C

MAX7359 toc01

MAX7359 toc04

GPO PORT OUTPUT LOW VOLTAGE

vs. SINK CURRENT

300

VCC = +3.0V

250

200

(mV)

150

OL

V

100

50

0

0105 15202530

TA = +85°C

= +25°C

T

A

I

(mA)

SINK

TA = -40°C

KEY-SWITCH SOURCE CURRENT

vs. SUPPLY VOLTAGE

22.0
COL0 = GND

21.5

21.0

20.5

KEY-SWITCH SOURCE CURRENT (μA)

20.0

1.6 3.6

TA = +85°C

TA = -40°C

TA = +25°C

3.22.82.42.0

SUPPLY VOLTAGE (V)

MAX7359 toc02

MAX7359 toc05

GPO PORT OUTPUT LOW VOLTAGE

vs. SINK CURRENT

300

VCC = +3.6V

250

200

(mV)

150

OL

V

100

50

0

0105 15202530

TA = +85°C

TA = +25°C

I

(mA)

SINK

TA = -40°C

SLEEP MODE SUPPLY CURRENT

vs. SUPPLY VOLTAGE

2.0

1.5

1.0

0.5

SHUTDOWN SUPPLY CURRENT (μA)

0

1.6 2.62.1 3.1 3.6
SUPPLY VOLTAGE (V)

MAX7359 toc03

MAX7359 toc06

MAX7359

2-Wire Interfaced Low-EMI

Key Switch Controller/GPO

_______________________________________________________________________________________ 5

Functional Block Diagram

INT

SDA

SCL

MAX7359

INTERFACE

TIMEOUT

*GPO

I2C

BUS

64kHz

OSCILLATOR

CONTROL

REGISTERS

FIFO

POR

KEY SCAN

COLUMN ENABLE

GPO ENABLE

CURRENT DETECT

ROW ENABLE

CL0
CL1

CURRENT

SOURCE

COLUMN

DRIVES

OPEN­DRAIN

ROW

DRIVES

CL2*
CL3*
CL4*
CL5*
CL6*
CL7*

RO0
RO1
RO2
RO3
RO4
RO5
RO6
RO7

MAX7359

2-Wire Interfaced Low-EMI
Key Switch Controller/GPO

6 _______________________________________________________________________________________

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
consumption. 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 micro­processor with too many interrupts. The key-switch sta­tus 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 config­ured 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 NAME FUNCTION

1 ROW2 Row Input from Key Matrix. Leave ROW2 unconnected or connect to GND if unused.

2 ROW3 Row Input from Key Matrix. Leave ROW3 unconnected or connect to GND if unused.

3 COL3/PORT3 Column Output to Key Matrix or GPO. Leave COL3/PORT3 unconnected if unused.

4 COL4/PORT4 Column Output to Key Matrix or GPO. Leave COL4/PORT4 unconnected if unused.

5 ROW4 Row Input from Key Matrix. Leave ROW4 unconnected or connect to GND if unused.

6 ROW5 Row Input from Key Matrix. Leave ROW5 unconnected or connect to GND if unused.

7 ROW6 Row Input from Key Matrix. Leave ROW6 unconnected or connect to GND if unused.

8 ROW7 Row Input from Key Matrix. Leave ROW7 unconnected or connect to GND if unused.

9 COL6/PORT6 Column Output to Key Matrix or GPO. Leave COL6/PORT6 unconnected if unused.

10 COL5/PORT5 Column Output to Key Matrix or GPO. Leave COL5/PORT5 unconnected if unused.

11 COL2/PORT2 Column Output to Key Matrix or GPO. Leave COL2/PORT2 unconnected if unused.

12 COL1 Column Output to Key Matrix. Leave COL1 unconnected if unused.

13 COL0 Column Output to Key Matrix. Leave COL0 unconnected if unused.

14 I.C. Internally Connected. Connect to GND for normal operation.

15 GND Ground

16 AD0 Adddress Input. ADO selects up to four device slave addresses (Table 10).

17 SDA I2C-Compatible, Serial-Data I/O

18 SCL I2C-Compatible, Serial-Clock Input
19 INT Active-Low Interrupt Output. INT is open drain.

20 V

21 N.C. No Connection. Not internally connected.

22 COL7/PORT7 Column Output to Key Matrix or GPO. Leave COL7/PORT7 unconnected is unused.

23 ROW0 Row Input from Key Matrix. Leave ROW0 unconnected or connect to GND if unused.

24 ROW1 Row Input from Key Matrix. Leave ROW1 unconnected or connect to GND if unused.

—EP

CC

Positive Supply Voltage. Bypass VCC to GND with a 0.047µF or higher ceramic capacitor.

Exposed Paddle. EP internally is connected to GND. Connect EP to a ground plane to increase
thermal performance.

MAX7359

2-Wire Interfaced Low-EMI

Key Switch Controller/GPO

_______________________________________________________________________________________ 7

Table 1. Key-Switch Mapping

Table 2. Register Address Map and Power-Up Condition

Key-Scan Controller

Key inputs are scanned statically, not dynamically, to
ensure low-EMI operation. As inputs only toggle in
response to switch changes, the key matrix can be
routed closer to sensitive circuit nodes.

The key controller debounces and maintains a FIFO of
key-press and release events (including autorepeated
key presses, if autorepeat is enabled). Table 1 shows
keys order.

_____________________Initial Power-Up

On power-up, all control registers are set to power-up
values and the MAX7359 is in sleep mode (Table 2).

Registers Description

Keys FIFO Register (0x00)

The keys FIFO register contains the information pertain­ing to the status of the keys FIFO, as well as the key
events that have been debounced (Table 3). Bits D0 to

D5 denote which of the 64 keys have been debounced
and the keys are numbered as in Table 1.

D7 indicates if there is more data in the FIFO except
when D5:D0 indicate key 63 or key 62. When D5:D0
indicate key 63 or key 62, the host should read one
more time to determine whether there is more data in
FIFO. It is better to use key 62 and key 63 for rarely
used keys. D6 indicates if it is a key-press or release
event except when D5:D0 indicate key 63 or key 62.

Reading the key-scan FIFO clears the interrupt INT
depending on the setting of bit D5 in the configuration
register (0x01).

Configuration Register (0x01)

The configuration register controls the I2C bus timeout
feature, enables key release detection, enables autowake,
and determines how INT should be deasserted. By writing
to bit D7, you can put the MAX7359 into sleep mode or
operating mode, however, autosleep and autowake,
when enabled, also change the status of this bit (Table 4).

PIN COL0 COL1 COL2/PORT2 COL3/PORT3 COL4/PORT4 COL5/PORT5 COL6/PORT6 COL7/PORT7

ROW0 KEY 0 KEY 8 KEY 16 KEY 24 KEY 32 KEY 40 KEY 48 KEY 56

ROW1 KEY 1 KEY 9 KEY 17 KEY 25 KEY 33 KEY 41 KEY 49 KEY 57

ROW2 KEY 2 KEY 10 KEY 18 KEY 26 KEY 34 KEY 42 KEY 50 KEY 58

ROW3 KEY 3 KEY 11 KEY 19 KEY 27 KEY 35 KEY 43 KEY 51 KEY 59

ROW4 KEY 4 KEY 12 KEY 20 KEY 28 KEY 36 KEY 44 KEY 52 KEY 60

ROW5 KEY 5 KEY 13 KEY 21 KEY 29 KEY 37 KEY 45 KEY 53 KEY 61

ROW6 KEY 6 KEY 14 KEY 22 KEY 30 KEY 38 KEY 46 KEY 54 KEY 62

ROW7 KEY 7 KEY 15 KEY 23 KEY 31 KEY 39 KEY 47 KEY 55 KEY 63

ADDRESS

CODE (hex)

0x00 Read only 0x3F Keys FIFO Read FIFO key scan data out

0x01 R/W 0x0A Configuration

0x02 R/W 0xFF Debounce Key debounce time setting and GPO enable
0x03 R/W 0x00 Interrupt INT frequency setting
0x04 R/W 0xFE Ports Ports 2–7 and INT GPO control
0x05 R/W 0x00 Key repeat Delay and frequency for key repeat
0x06 R/W 0x07 Sleep Idle time to autosleep

READ/WRITE

POWER-UP VALUE

(hex)

REGISTER
FUNCTION

DESCRIPTION

Power down, key release enable, autowakeup, and

2

I

C timeout enable