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2-Wire Interfaced Low-EMI Key Switch and Sounder Controllers

Product Details

Key Features

Simplified Block Diagram

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

Applications/Uses

  • Industrial Controls
  • Instrumentation Panels
  • Medical Instruments
  • Security and Access

Description

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 1kΩ.

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.

Simplified Block Diagram

MAX7347, MAX7348, MAX7349: Typical Application Circuit MAX7347, MAX7348, MAX7349: Typical Application Circuit Zoom icon

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .

Sampling:
Selecting the Sample button above will redirect to the third-party ADI Sample Site. The part selected will carry over to your cart on this site once logged in. Please create a new account there if you have never used the site before. Contact SampleSupport@analog.com with any questions regarding this Sample Site.