The ADP5588 mobile I/O expander and QWERTY keypad controller from Analog Devices provides ambient light sensing for smart portable devices that require a large keypad matrix and expanded I/O lines. It also integrates keypad scanning, de-bouncing, and interrupt generation, resulting in reduced processor I/Os and loading. By detecting ambient-light conditions, processors can ensure efficient control of keypad backlighting to significantly reduce power consumption and extend battery life by 20% to 50%, depending on the usage model, according to ADI.

Article Tools

• 

Today’s baseband or applications processors often are I/O limited due to the ever-increasing functions that smart portable devices provide. The ADP5588 enables to processor to control up to an additional 15 general-purpose I/Os (GPIO) through the I2C-compatible bus, reducing direct processor routing from 18 lines to three. For greater flexibility, the CPU can communicate to the ADP5588 through the I2C-compatible serial interface to reconfigure the row and column pins as general-purpose input, general-purpose output, or light-sensor input pins depending on the application.

The ADP5588 offloads key-scan and GPIO functions from the CPU, freeing up the processor for higher-priority functions and saving energy. A key even counter with overflow interrupt capability allows the device to manage up to 10 unprocessed key events, while a key-lock option permits designers to choose whether or not to issue a key-press interrupt when the lock is active. The device manages all mobile key scanning and decoding functions by storing the key presses and releases and flagging them to the processor via a single interrupt line and two I2C-compatible interface lines. Designers can then minimize the number of control lines from the microprocessor for significant cost and reliability benefits.

Samples are now available in a 4- by 4-mm, 24-pin lead-frame chip-scale package (LFCSP). The ADP5588 supports 1.8- to 3.0-V operation. It costs $1.08 each in 1000-unit quantities.

Analog Devices