I²C-Interfaced Key-Switch Controller and LED Driver/GPIOs with Integrated ESD Protection

The 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 5kΩ. 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 (1µA typ) after a sleep timeout period. The autowake feature configures the MAX7360 to return to normal operating mode from sleep upon a keypress.

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 20mA. 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 (5mm x 5mm) 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.

Applications

* Cell Phones

* Handheld Games

* Instrumentation

* PDAs

* Portable Consumer Electronics

* Printers

* Integrated ESD Protection

* ±8kV IEC 61000-4-2 Contact Discharge

* ±15kV IEC 61000-4-2 Air-Gap Discharge

* +14V Tolerant, Open-Drain I/O Ports Capable of Constant-Current LED Drive

* Rotary Switch-Capable Input Pair (PORT6, PORT7)

* 256-Step PWM Individual LED Intensity Control

* Individual LED Blink Rates and Common LED Fade In/Out Rates from 256ms to 4096ms

* FIFO Queues Up to 16 Debounced Key Events

* User-Configurable Key Debounce (9ms to 40ms)

* Keyscan Uses Static Matrix Monitoring for Low EMI Operation

* +1.62V to +3.6V Operation

* Monitors Up to 64 Keys

* Key-Switch Interrupt (Active-Low INTK) on Each Debounced Event/FIFO Level, or End of Definable Time Period

* Port Interrupt (Active-Low INTI) for Input Ports for Special-Key Functions

* 400kbps, +5.5V Tolerant 2-Wire Serial Interface with Selectable Bus Timeout

* Four I²C Address Choices