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General Description

The MAX7359 I

C interfaced peripheral provides micro-

processors 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 fur-

ther 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-pur-

pose 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

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

Ordering Information

19-0850; Rev 0; 7/07

EVALUATION KIT

AVAILABLE

PART

TEMP

RANGE

PIN-PACKAGE

PKG

CODE

MAX7359ETG+

-40°C to

+85°C

24 TQFN-EP*

(3.5mm x 3.5mm)

T243A3-1

Denotes a lead-free package.

EP = Exposed paddle.

MAX7359

COL_

GND

SCL

SDA

AD0

ROW_

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.

Summary of content (22 pages)

PAGE 1
9-0850; Rev 0; 7/07 KIT ATION EVALU E L B AVAILA 2-Wire Interfaced Low-EMI Key Switch Controller/GPO Features The MAX7359 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.
PAGE 2
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND.) VCC ..........................................................................-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 (VCC + 0.3V) DC Current on COL2/PORT2–COL7/PORT7 ......................
PAGE 3
2-Wire Interfaced Low-EMI Key Switch Controller/GPO (VCC = 1.62V to 3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 2.5V, TA = +25°C.) (Notes 1, 2) (Figure 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 10 pF 400 kHz Input Capacitance (SCL, SDA, AD0) CIN (Notes 3, 4) SCL Serial-Clock Frequency fSCL Bus timeout disabled Bus Free Time Between a STOP and a START Condition tBUF 1.3 µs Hold Time (Repeated) START Condition tHD, STA 0.
PAGE 4
Typical Operating Characteristics (VCC = 2.5V, TA = +25°C, unless otherwise noted.) 250 VCC = +3.0V 300 250 MAX7359 toc03 VCC = +2.4V MAX7359 toc02 300 MAX7359 toc01 300 GPO PORT OUTPUT LOW VOLTAGE vs. SINK CURRENT GPO PORT OUTPUT LOW VOLTAGE vs. SINK CURRENT GPO PORT OUTPUT LOW VOLTAGE vs. SINK CURRENT VCC = +3.
PAGE 5
2-Wire Interfaced Low-EMI Key Switch Controller/GPO MAX7359 COLUMN ENABLE 64kHz OSCILLATOR GPO ENABLE CURRENT DETECT CURRENT SOURCE COLUMN DRIVES INT SDA SCL I2C INTERFACE CONTROL REGISTERS FIFO KEY SCAN ROW ENABLE BUS TIMEOUT POR CL0 CL1 CL2* CL3* CL4* CL5* CL6* CL7* OPENDRAIN ROW DRIVES RO0 RO1 RO2 RO3 RO4 RO5 RO6 RO7 *GPO _______________________________________________________________________________________ 5 MAX7359 Functional Block Diagram
PAGE 6
2-Wire Interfaced Low-EMI Key Switch Controller/GPO MAX7359 Pin Description PIN NAME 1 ROW2 Row Input from Key Matrix. Leave ROW2 unconnected or connect to GND if unused. FUNCTION 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.
PAGE 7
2-Wire Interfaced Low-EMI Key Switch Controller/GPO _____________________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.
PAGE 8
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO Table 3. Keys FIFO Register Format (0x00) SPECIAL FUNCTION KEYS FIFO REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 FIFO empty flag Key release flag X X X X X X FIFO is empty. 0 0 1 1 1 1 1 1 FIFO is overflow. Continue to read data in FIFO. 0 1 1 1 1 1 1 1 Key 63 is pressed. Read one more time to determine whether there is more data in FIFO. 1 0 1 1 1 1 1 1 Key 63 is released.
PAGE 9
2-Wire Interfaced Low-EMI Key Switch Controller/GPO MAX7359 Table 4. Configuration Register Format (0x01) REGISTER BIT DESCRIPTION VALUE D6 0 1 Operating mode 0 This bit must always be 0. Improper operation may result by writing a 1 to this location. 0 Clear when FIFO empty Clear after host read. In this mode, I2C should read FIFO until interrupt condition removed, or further INT may be lost. 0 This bit must always be 0. Improper operation may result by writing a 1 to this location.
PAGE 10
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO Debounce Register (0x02) The debounce register sets the time for each debounce cycle, as well as setting whether the GPO ports are enabled or disabled. Bits D0 through D4 set the debounce time in increments of 1ms starting at 9ms and ending at 40ms (Table 5). Bits D5 through D7 set which of the GPO ports is enabled. Note the GPO ports can be enabled only in the combinations shown in Table 5, from all disabled to all enabled. Table 5.
PAGE 11
2-Wire Interfaced Low-EMI Key Switch Controller/GPO D4 to an appropriate value, the interrupt can be asserted at the end of the selected number of debounce cycles following a key event (Table 6). This number ranges from 1 to 31 debounce cycles. The FIFO based interrupt can be configured to assert INT when there are between 4 through 16 key events stored in the FIFO. Bits D7 through D5 set the FIFO based interrupt.
PAGE 12
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO Table 7.
PAGE 13
2-Wire Interfaced Low-EMI Key Switch Controller/GPO Autosleep Register (0x06) Autosleep puts the MAX7359 in sleep mode to draw minimal current. When enabled, the MAX7359 enters sleep mode if no keys are pressed for the autosleep time (Table 9). Sleep Mode In sleep mode, the MAX7359 draws minimal current. Switch matrix current sources are turned off and pulled up to VCC. Writing a 0 to D7 in the configuration register (0x01) puts the device in sleep mode.
PAGE 14
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO tR SDA tSU, DAT tLOW tSU, STA tF tF,TX tBUF tHD, STA tSU, STO tHD, DAT tHIGH SCL tHD, STA tR tF START CONDITION REPEATED START CONDITION STOP CONDITION START CONDITION Figure 1. 2-Wire Serial Interface Timing Details SDA SCL S P START CONDITION STOP CONDITION Figure 2. Start and Stop Conditions SDA SCL DATA LINE STABLE; DATA VALID CHANGE OF DATA ALLOWED Figure 3.
PAGE 15
2-Wire Interfaced Low-EMI Key Switch Controller/GPO The MAX7359 monitors the bus continuously, waiting for a START condition followed by its slave address. When the MAX7359 recognizes its slave address, it acknowledges and is then ready for continued communication.
PAGE 16
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO COMMAND BYTE IS STORED ON RECEIPT OF ACKNOWLEDGE CONDITION ACKNOWLEDGE FROM MAX7359 S SLAVE ADDRESS 0 D7 D6 D5 A D4 D3 D2 D1 D0 COMMAND BYTE R/W A P ACKNOWLEDGE FROM MAX7359 Figure 6.
PAGE 17
2-Wire Interfaced Low-EMI Key Switch Controller/GPO D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 ACKNOWLEDGE FROM MAX7359 S SLAVE ADDRESS 0 A COMMAND BYTE R/W A DATA BYTE A P N BYTES AUTOINCREMENT COMMAND BYTE ADDRESS Figure 8. N Data Bytes Received Command Address Autoincrementing Address autoincrementing allows the MAX7359 to be configured with fewer transmissions by minimizing the number of times the command address needs to be sent.
PAGE 18
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO REGULAR KEY-PRESS EVENT EXAMPLES OF VALID THREE-KEY COMBINATIONS GHOST-KEY EVENT KEY-SWITCH MATRIX Figure 9. Ghost-Key Phenomenon KEY-SWITCH MATRIX KEY-SWITCH MATRIX Figure 10.
PAGE 19
2-Wire Interfaced Low-EMI Key Switch Controller/GPO 3.3V 3.3V 1.
PAGE 20
2-Wire Interfaced Low-EMI Key Switch Controller/GPO MAX7359 Pin Configuration 16 COL0 AD0 17 GND SDA 18 I.C. SCL TOP VIEW 15 14 13 INT 19 12 COL1 VCC 20 11 COL2/PORT2 N.C.
PAGE 21
2-Wire Interfaced Low-EMI Key Switch Controller/GPO 24L THIN QFN.EPS ______________________________________________________________________________________ 21 MAX7359 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.
PAGE 22
MAX7359 2-Wire Interfaced Low-EMI Key Switch Controller/GPO Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.