MAX7360 Keypad Controller

By Maxim Integrated 250

MAX7360 Keypad Controller

Maxim's MAX7360 I2C-interfaced peripheral provides microprocessors with management of up to 64 key switches, with an additional eight LED drivers/GPIOs that feature constant-current, PWM intensity control, and rotary switch control options.

The key-switch drivers interface with metallic or resistive switches with on-resistances up to 5 kΩ. Key inputs are monitored statically, not dynamically, to ensure low-EMI operation. The MAX7360 features autosleep and autowake modes to further minimize the power consumption of the device. The autosleep feature puts the device in a low-power state (1 µA typ) after a sleep timeout period. The autowake feature configures the MAX7360 to return to normal operating mode from sleep upon a key press.

The key controller debounces and maintains a FIFO of keypress and release events (including autorepeat, if enabled). An interrupt (active-low INTK) output can be configured to alert keypresses, as they occur, or at maximum rate.

There are eight open-drain I/O ports, which can be used to drive LEDs. The maximum constant-current level for each open-drain port is 20 mA. The intensity of the LED on each open-drain port can be individually adjusted through a 256-step PWM control. An input port pair (PORT6, PORT7) can be configured to accept 2-bit gray code inputs from a rotary switch. In addition, if not used for key-switch control, up to six column pins can be used as general-purpose open-drain outputs (GPOs) for LED drive or logic control.

The MAX7360 is offered in a 40-pin (5 mm x 5 mm), thin QFN package with an exposed pad, and a small 36-bump wafer level package (WLP) for cell phones, pocket PCs, and other portable consumer electronic applications. The MAX7360 operates over the -40°C to +85°C extended temperature range.

  • Integrated ESD protection
  • ±8 kV IEC 61000-4-2 contact discharge
  • ±15 kV IEC 61000-4-2 air-gap discharge
  • Rotary switch-capable input pair (PORT6, PORT7)
  • 256-Step PWM individual LED intensity control
  • FIFO queues up to 16 debounced key events
  • User-configurable key debounce (9 ms to 40 ms)
  • Keyscan uses static matrix monitoring for low EMI operation
  • +1.62 V to +3.6 V operation
  • Monitors up to 64 keys
  • Four I2C address choices
  • +14 V tolerant, open-drain I/O ports capable of constant-current LED drive
  • Individual LED blink rates and common LED fade In/Out rates from 256 ms to 4096 ms
  • Port interrupt (active-low INTI) for input ports for special-key functions
  • 400 kbps, +5.5 V tolerant 2-wire serial interface with selectable bus timeout
  • Key-switch interrupt (active-low INTK) on each debounced event/FIFO level, or end of definable time period
  • Cell phones
  • Handheld games
  • Instrumentation
  • PDAs
  • Portable consumer electronics
  • Printers

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