2-Wire Interfaced Low-EMI Key Switch Controller/GPO

The MAX7359 I²C 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.

The MAX7359 features autosleep and autowake to further 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 (active-low 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 active-low INT, if not used, can function as a general-purpose output (GPO).

The MAX7359 is offered in small, 24-pin TQFN (3.5mm x 3.5mm) and 25-bump WLP (2.31mm x 2.31mm) packages 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 * Handheld Games * PDAs * Portable Consumer Electronics

* 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 I²C Address Choices

* Small, 24-Pin TQFN Package (3.5mm x 3.5mm) , or 25-Pin WLP Package (2.31mm x 2.31mm)