Freescale proximity sensors accelerate touch-control design for portable terminals

To realize such a design, sensitive and accurate touch sensors are essential, because such devices enable the touch panel to respond to commands promptly and reliably.

To meet the market demand for touch sensing control, Freescale Semiconductor, as a leading sensor device designer and manufacturer, has launched two highly sensitive touch panel controller products - MPR081 and MPR082 proximity capacitive touch sensor controllers, which can detect touch by measuring capacitance.

As touch sensing technology becomes more popular, sensor-driven interfaces become more intuitive and easier to use than before, and the way users use mobile electronic devices is also changing. In order to help manufacturers meet the challenges of touch control design and accelerate their R&D cycle, Freescale's touch sensing controller provides the necessary functions and pin designs for implementing rotation and touch panel layout. The device's flexible use of electrodes can bring multiple sensing touch points to the next generation of consumer electronics.

How a Proximity Capacitive Touch Sensing Controller Works

Touch sensors are becoming a necessity for any interface with buttons. They provide designers with a low-cost way to replace mechanical switch buttons in a variety of applications such as access control, appliances, mobile phones, MP3 players, PC peripherals, and remote controls. Using touch-sensitive controls instead of traditional switch-button interfaces ultimately makes the interface more intuitive and easier to use.

"More and more control panel manufacturers are using intelligent touch controls in their interface designs to enable more advanced functionality in portable electronics and appliances," said Demetre Kondylis, vice president and general manager of Freescale's Sensor and Actuator Solutions Division. "The MPR081 and MPR082 proximity sensors enable designers to improve user interfaces and provide greater flexibility for the next generation of consumer electronics."

Figure 1 The MPR081 proximity sensor is a user interface controller that handles a 16-quadrant rotary touch pad.

Figure 2 The MPR082 proximity sensor is a user interface controller that can handle 20 touch pads

Freescale's MPR081 and MPR082 proximity capacitive touch sensor controllers detect touch by measuring capacitance. The MPR081 proximity sensor is a user interface controller that handles a 16-quadrant rotary touch pad, ideal for rotary interface applications, while the MPR082 proximity sensor is a user interface controller that can handle 20 touch pads, ideal for touch pad applications. They both use an I2C interface to communicate with the host, and can be configured to run and interrupt to indicate changes in status to the host.

The MPR081 and MPR082 feature a piezoelectric sounder that provides audible feedback, simulating the click of a mechanical button. The proximity sensors share the same pin layout, simplifying control panel management, switch replacement, rotary and linear slide switches, and touchpad implementation. Both touch sensor devices communicate using a digital output I2C interface and operate in the 1.8V to 3.6V voltage range, an ideal voltage range for consumer electronics.

Advantages of proximity detection compared to traditional designs

Proximity detection provides the latest technology for users to interact with consumer electronics. Touch sensing is one of the most popular applications and design hotspots because it:

· Ability to eliminate mechanical buttons and slide switches;
· Improve reliability by eliminating mechanical wear;
· Provide greater flexibility for product designers;
· Reduce total system cost;
· Intuitively achieve automation through our fingers.

For example, the MPR081 and MPR082 proximity sensors can be used on the front panel of a washing machine to replace mechanical knobs and push-button switches. The user approaches the command displayed on the panel with their finger, and the washing machine begins to perform the requested function.

Replacing mechanical buttons on smart portable electronic devices allows for larger LCD display sizes and placement options. In addition, the proximity sensor electrode layout can be easily changed depending on the device's portrait and landscape modes.

Technical features of MPR081 and MPR082

·Operates from 1.8V to 3.6V.
·150 μA average current (all touchpads monitored);
·1 μA standby current;
·MPR081 supports a total of 16 positions of the rotary interface;
·MPR082 can control up to 20 touchpads;
·Unique false touch rejection technology;
·Long-term panel analysis and detection, without reset due to EMI events;
·Audio device driver provides audible feedback for simulated mechanical buttons;
·Digital output (I2C, with custom addressing);
·16-pin QFN and TSSOP packages;
·-40℃ to +85℃ operating temperature range.

Pricing and Availability

For sample availability information for the MPR081 and MPR082, please contact Freescale sales. General availability is expected in the fourth quarter of 2007. Suggested retail pricing for both products starts at $1.07 in 10,000-unit quantities. Suggested pricing for consumer quantities is less than $1.

Freescale provides evaluation kits to demonstrate the key features of proximity sensors to help shorten the development cycle. The KITMPR081EVM for MPR081 and the KITMPR082EVM for MPR082 will be available soon, with a suggested retail price of $99 each.