MICROCONTROLLER SOLUTIONS

ICs Provide Expansion for Mobile Platforms

STMicroelectronics' Xpander Logic family of devices is designed to increase the number of I/O ports and enhance the control and mixed-signal capabilities of existing microcontrollers and microprocessors. The range now includes support for touch key interfaces, with the recent launch of the STMPE1208 12-channel capacitive touch key sensor device.

Supplied in a 5mm x 5mm QFN package, the STMPE1208 offers fast and accurate capacitive sensing at extremely low power, with operating current 98µA in active mode and 60µA in idle mode. The device includes an automatic impedance calibration feature to ensure that changes in the environment will not affect operation of the touch keys. With a fully digital architecture and advanced filtering system, the STMPE1208 is ElectroStatic Discharge (ESD) tested to 8kV Human Body Model (HBM).

The Xpander Logic family allows designers to add features to devices such as mobile phones and Portable Media Players (PMP), without the need to upgrade the MCU itself. Supplied in very small packages (QFN16, µTFBGA25 and µTFBGA36), the devices feature ultra low power consumption and can adapt flexibly to various interface voltages.

Available functions include a sophisticated matrix keypad controller supporting up to 96 keys; an advanced PWM controller that is capable of complex brightness-pattern control; and a three-wire rotating wheel interface providing motion detection and monitoring/buffering features. The family also integrates an Analogue-to-Digital Converter (ADC) and a Digital-to-Analogue Converter (DAC). This can be used to implement a wide range of mixed signal features such as providing an automatic dimming unit that lets an ambient light sensor control a backlight without CPU intervention.



Communication between the Central Processor Unit (CPU) and Xpander Logic IC is via a standard, high-speed Inter-Integrated Circuit (I²C) serial peripheral interface. As well as allowing design teams to extend the lifetime of existing products, these devices can help to overcome limits on the number of Input/Output (I/O) ports in new microcontroller and microprocessor-based embedded designs.

Xpander Logic devices are available with four, eight, 16 or 24 I/Os. Options include the ability to configure each line as input or output, open drain output pins, standard or fast I²C operation and a reset pin. In line with their use in mobile applications, devices require a 'suspend' current of as little as 1µA and can operate from voltages between 1.65V and 3.6V. A 'wake up' function on each I/O further increases flexibility in application.

Features

• Range of port expansion ICs with four, eight, 16 or 24 I/Os
• Very small packages (QFN16, TFBGA25 and TFBGA36)
• Ultra low power consumption
  • Suspend mode as low as 1µA
• Standard I²C interface
• Flexible interface voltage on I/Os
• Intelligent features
  • Touch key control
  • Keypad controller
  • PWM controller
  • Rotator controller
  • ADC/DAC and automatic dimming
• Open-drain interrupt output pin
• Reset pin
• Supports 'wake up on event' implementations

Applications

• Mobile phones, smart phones and IP phones
• Multi-function printers
• Portable multimedia devices
• Game console
• Industrial user interfaces
• Addition of functions in embedded applications
  • Touch key
  • QWERTY keypad
  • Analogue/PWM
  • Backlight/LED brightness control
  • Ambient light sensing

For further information, including a User Manual, Datasheets, and the Xpander Logic Presentation, please click here