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General Description

The MAX7347/MAX7348/MAX7349 I

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

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

C Address Choices

♦ Selectable 2-Wire Serial Bus Timeout

♦ Under 10µA Shutdown Current

MAX7347/MAX7348/MAX7349

2-Wire Interfaced Low-EMI Key Switch

and Sounder Controllers

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-3556; Rev 5; 5/07

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX7347AEE+ -40°C to +125°C 16 QSOP

E16-4

MAX7347ATE+ -40°C to +125°C 16 TQFN-EP*

T1644-4

MAX7348AEP+ -40°C to +125°C 20 QSOP

E20-1

MAX7349AEG+ -40°C to +125°C 24 QSOP

E24-1

MAX7349ATG+ -40°C to +125°C 24 TQFN-EP*

T2444-4

Denotes lead-free package.

EP = Exposed paddle.

MAX7349

V+

COL_

SOUNDER

GND

SCL

SDA

AD0

ALERT

ROW_

PIEZO

TRANSDUCER

SWITCH

ARRAY, UP

TO 64

SWITCHES

INPUT

2.4V TO 3.6V

INT

Typical Application Circuit

Pin Configurations appear at end of data sheet.

Summary of content (29 pages)

PAGE 1
9-3556; Rev 5; 5/07 KIT ATION EVALU E L B A AVAIL 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers I2C The MAX7347/MAX7348/MAX7349 interfaced peripherals 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.
PAGE 2
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers 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 ..........
PAGE 3
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers (V+ = 2.4V to 3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at V+ = 3.3V, TA = +25°C.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 10 pF Input Capacitance (SCL, SDA, AD0) CIN SCL Serial Clock Frequency fSCL Bus Free Time Between a STOP and a START Condition tBUF 1.3 µs Hold Time (Repeated) START Condition tHD, STA 0.6 µs Repeated START Condition Setup Time tSU, STA 0.
PAGE 4
Typical Operating Characteristics (V+ = 3.3V, TA = +25°C, unless otherwise noted. Supply range for V+ is 2.4V to 3.6V. Temperature range is -40°C to +125°C.) 250 300 200 100 TA = +125°C VOL (V) 150 150 TA = -40°C TA = +25°C 50 0 5 10 15 20 25 0 0 5 10 15 20 0 25 5 10 15 SUPPLY CURRENT vs. SUPPLY VOLTAGE KEY-SWITCH SOURCE CURRENT vs. SUPPLY VOLTAGE SOUNDER FREQUENCY vs.
PAGE 5
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers PIN MAX7347 MAX7347 MAX7349 MAX7349 MAX7348 (QSOP) (TQFN) (QSOP) (TQFN) NAME FUNCTION Row Input from Key Matrix. Leave open circuit if unused. 1 15 1 2 23 ROW0 2 16 2 3 24 ROW1 Row Input from Key Matrix. Leave open circuit if unused. 3 1 3 4 1 ROW2 Row Input from Key Matrix. Leave open circuit if unused. 4 2 4 5 2 ROW3 Row Input from Key Matrix. Leave open circuit if unused.
PAGE 6
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Table 1. Product Features Table PART PACKAGEPINS MAXIMUM KEY SWITCHES INT OUTPUT KEYSCAN SLAVE IDs SOUNDER SLAVE IDs SOUNDER OUTPUT GPOs ALERT INPUT MAX7349 24 64 Yes 4 4 Yes 6 + 1 (INT) Yes MAX7348 20 40 Yes 4 4 Yes 3 + 1 (INT) — MAX7347 16 24 Yes 1 fixed — — 1 + 1 (INT) — too many interrupts. The key-switch status can be checked at any time by reading the key-switch FIFO.
PAGE 7
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers MAX7347/MAX7348/MAX7349 *MAX7348 AND MAX7349 ONLY. **MAX7349 ONLY.
PAGE 8
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers SDA tSU, DAT tLOW tSU, STA tBUF tHD, STA tSU, STO tHD, DAT tHIGH SCL tHD, STA tR tF START CONDITION REPEATED START CONDITION STOP CONDITION START CONDITION Figure 2. 2-Wire Serial Interface Timing Details SDA SCL S P START CONDITION STOP CONDITION Figure 3. Start and Stop Conditions SDA SCL DATA LINE STABLE; DATA VALID CHANGE OF DATA ALLOWED Figure 4.
PAGE 9
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers 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 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
PAGE 10
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers START CONDITION CLOCK PULSE FOR ACKNOWLEDGE 1 SCL 2 8 9 SDA BY TRANSMITTER SDA BY RECEIVER S Figure 5. Acknowledge SDA 0 1 1 1 MSB A3 A2 A1 R/W ACK LSB SCL Figure 6.
PAGE 11
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers S SLAVE ADDRESS D7 0 R/W D6 D5 A D4 D3 D2 D1 D0 COMMAND BYTE A P ACKNOWLEDGE FROM MAX7347/MAX7348/MAX7349 Figure 7.
PAGE 12
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Table 5.
PAGE 13
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers D15 D14 D13 D12 D11 D10 D9 D8 ADDRESS CODE (hex) Keys FIFO 0 0 0 0 0 0 0 0 0x00 Debounce 0 0 0 0 0 0 0 1 0x01 Autorepeat 0 0 0 0 0 0 1 0 0x02 COMMAND ADDRESS REGISTER FUNCTION Interrupt 0 0 0 0 0 0 1 1 0x03 Configuration 0 0 0 0 0 1 0 0 0x04 Ports 0 0 0 0 0 1 0 1 0x05 Key Sound 0 0 0 0 0 1 1 0 0x06 Alert Sound 0 0 0 0 0 1 1 1 0x07 Table 8.
PAGE 14
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Table 9.
PAGE 15
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Interrupt Register The interrupt register contains information related to the settings of the interrupt request function, as well as the status of the INT output, which can also be configured as a GPO. Bits D0 through D4 set the key-scan interrupt frequency. By setting bits D0 through D4 to an appropriate value, the interrupt can be asserted at the end of the selected number of debounce cycles (Table 11).
PAGE 16
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Table 10.
PAGE 17
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers REGISTER INTERRUPT REGISTER ADDRESS CODE (hex) 0x03 REGISTER DATA D7 D6 D5 INT STATUS* ALERT EVENT* KEYSCAN EVENT* D4 D3 D2 D1 D0 KEY-SCAN INTERRUPT FREQUENCY Current INT is due to key-scan event(s) 0x03 1 0 1 X X X X X Current INT is due to alert event 0x03 1 1 0 X X X X X Current INT is due to both key-scan event(s) and alert event 0x03 1 1 1 X X X X X INT has not been asserted 0x03 0 0 0 X X
PAGE 18
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Table 12.
PAGE 19
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers REGISTER DATA REGISTER ADDRESS CODE (hex) D7 CONFIGURATION REGISTER 0x04 SHUTDOWN Shutdown mode; key-scan and sounder timing are disabled, interrupts disabled, but alert input can be read and port outputs (as selected) can be changed 0x04 0 X X X X X X X Operating mode; key scan is started, and commands in sounder queue are actioned 0x04 1 X X X X X X X Power-up default setting 0x04 0 0 0 0 0 0 0 1 D6 D5 D4
PAGE 20
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Table 13.
PAGE 21
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers REGISTER ADDRESS CODE (hex) This 8-bit value is passed to sounder controller on the falling edge of the alert input; these 7 bits define duration and frequency only; sounder command bit D0 is ignored and fixed internally at 1; if an alert sound is sent as 000xxxxx (continuous), then the command is stored as 111xxxxx (1000 ms) 0x07 Power-up default setting 0x07 REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0 7-bit value (see Table 16 for funct
PAGE 22
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Table 16. Sounder Register Format (continued) REGISTER DATA REGISTER READ WRITE SOUNDER REGISTER D7 D6 D5 DURATION D4 D3 D2 FREQUENCY D1 D0 LEVEL BUFFER Sounder output active low for sound duration; queue cleared — Write 0 0 0 0 0 Sounder output active high for sound duration; queue cleared — Write 0 0 0 1 0 Sound frequency is 523.
PAGE 23
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers Shutdown The MAX7347/MAX7348/MAX7349 are put into shutdown mode by clearing bit D7 in the configuration register (Table 12). In shutdown, the key-scan controller and sounder controller are both disabled, and the MAX7347/MAX7348/MAX7349 draw minimal current. No additional supply current is drawn if any keys are pressed.
PAGE 24
MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers REGULAR KEY-PRESS EVENT EXAMPLES OF VALID THREE-KEY COMBINATIONS GHOST-KEY EVENT KEY-SWITCH MATRIX KEY-SWITCH MATRIX KEY-SWITCH MATRIX Figure 10. Ghost-Key Phenomenon Figure 11. Valid Three-Key Combinations VCC 50kΩ BIAS SHDN OUT- SHUTDOWN 50kΩ 10kΩ 16Ω IN+ 10kΩ OUT+ 0.22μF SOUNDER OUTPUT 2.61kΩ 21.5kΩ 32.4kΩ IN- 68nF MAX4366 22nF 220pF 21.5kΩ Figure 12.
PAGE 25
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers 3.3V 3.3V KEY 0 KEY 8 KEY 16 KEY 1 KEY 9 KEY 17 KEY 2 KEY 10 KEY 18 KEY 3 KEY 11 KEY 19 KEY 4 KEY 12 KEY 20 KEY 5 KEY 13 KEY 21 KEY 6 KEY 14 KEY 22 KEY 7 KEY 15 KEY 23 3.
PAGE 26
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers MAX7347/MAX7348/MAX7349 Pin Configurations TOP VIEW ROW0 1 + 16 V+ ROW1 2 15 INT TOP VIEW 14 SCL ROW2 3 MAX7347 ROW3 4 13 SDA 12 GND ROW4 5 ROW5 6 11 COL0 ROW6 7 10 COL1 + COL7/PORT7 1 24 ALERT ROW0 2 23 V+ ROW1 3 22 INT ROW2 4 21 SCL MAX7349 ROW3 5 GND COL0 12 11 10 9 INT 13 8 COL1 V+ 14 7 COL2/PORT2 6 ROW7 5 ROW6 MAX7347 ROW0 15 ROW1 16 EP* + COL3/PORT3 6 19 AD0 COL4/PORT4 7 18 GND ROW4 8 17 SOU
PAGE 27
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers QSOP.EPS PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH 21-0055 F 1 1 ______________________________________________________________________________________ 27 MAX7347/MAX7348/MAX7349 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 28
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.) 24L QFN THIN.EPS MAX7347/MAX7348/MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.
PAGE 29
2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm 21-0139 E 2 2 Revision History Pages changed at Rev 5: 1, 2, 23, 29 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.