MAX7347, MAX7348, MAX7349 2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers

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The MAX7347/MAX7348/MAX7349 I²C 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. The switches can be metallic or resistive (carbon) up to 1k Ohm

.

The key controller debounces and maintains a FIFO of key-press events (including autorepeat, if enabled). An interrupt (active-low 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 programmed 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.

Key Features

Applications/Uses

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 I²C Address Choices
Selectable 2-Wire Serial Bus Timeout
Under 10µA Shutdown Current

	Industrial Controls
	Instrumentation Panels
	Medical Instruments
	Security and Access

Key Specifications: Keyswitch Controllers

Part Number

Interface

Max. Keys

I²C Interface Voltage

Typ. Supply Current (µA)

Typ. Shutdown Current (µA)

INT Output

Key Scan I²C Slave IDs

Sounder I²C Slave IDs

Sounder Output

GPOs

ALERT Input

Supply Voltage (V)

RoHS Available

Package

Smallest Available Package (max w/pins) (mm²)

Operating Temp. Range (°C)

Price^**

MAX7347

Serial 2-Wire 400kbit

2.4 to 5.5

7.5

Yes

6 + 1(INT)

Yes

2.4 to 3.6

Yes

QSOP/16
THIN QFN/16

-40 to +125

$1.35 @ 1k

MAX7348

Yes

3 + 1(INT)

QSOP/20

$1.55 @ 1k

MAX7349

1 + 1(INT)

QSOP/24
THIN QFN/24

$1.79 @ 1k

See All Keyswitch Controllers (3)

Notes:
^**This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized distributor.