Logic family overcomes limited number of I/O ports in micro-based embedded systems

16th March 2007
ES Admin
STMicroelectronics has introduced the Xpander Logic family to help customers overcome the limited number of I/O ports in microcontroller and microprocessor-based embedded systems. Any existing or additional I/O-intensive tasks on the central processing unit (CPU) can be now reassigned to the Xpander Logic IC that operates off ultra-low power and comes in a very small package, making it ideal for portable multimedia devices such as mobile phones, smartphones, and personal digital assistants.
The Xpander Logic family allows the existing system processor to use a wide range of intelligent functions through a standard and high-speed Inter-Integrated Circuit (I2C) serial peripheral interface. These intelligent features include a keypad controller, supporting 96 keys maximum, and a Pulse-Width Modulation (PWM) controller, able to adjust the brightness of the LEDs in addition to performing sophisticated brightness patterns. The Xpander Logic family also offers a 3-wire rotating-wheel controller which supports the increasingly popular rotating wheel interface in portable electronics by detecting the motion of the wheel and providing monitoring/buffering features. The family also integrates an Analog-to-Digital Converter (ADC) and a Digital-to-Analog Converter (DAC), allowing the host system to implement a wide range of mixed-signal features while providing an automatic dimming unit that lets the ambient light sensor control a backlight unit without CPU intervention.

All these features are achieved through a minimum change on the existing microprocessor or microcontroller firmware. As a result, the family is a very flexible and cost-competitive solution to expand system resources if compared to the complex implementation of larger and more expensive CPU or programmable logic devices in the embedded system.

A further benefit of the Xpander Logic family for users is the high optimization for micro-power operation and the advanced power-management support that helps modern portable systems preserve and extend battery life.

In production now, the devices are housed in very small packages (QFN16, microTFBGA25 and microTFBGA36). The Xpander Logic STMPE2401 provides all the above-mentioned intelligent functions in a microTFBGA36 package, while the STMPE801 performs the basic I/O expander function in a QFN16 package. The STMPE2401 and STMPE801 cost $1.5 and $0.80, respectively, in 100,000 unit quantities.

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