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Kionix Accelerometers & Evaluation Kits

The KX Series is a high performance, silicon micro machined, linear accelerometer is based on a sensor element and ASIC packaged in a standard 16-pin SOIC wide body package. The sensor element is fabricated from single crystal silicon with proprietary plasma processes and the element is protected by a silicon cap wafer that is attached at the wafer level and forms a hermetic seal. The sensor element functions on the principle of a differential capacitance component, which utilizes common mode cancellation to decrease errors from process variation and environmental stress.

The element is designed to provide a high signal to noise ratio and will satisfy applications for ±2g to ±250g ranges. The change of the sensor element capacitance with acceleration is detected and transformed into voltage by a c/v converter that consists of a charge amplifier and an additional switched capacitor integrator that form an electronic feedback circuit implemented in a standard CMOS technology ASIC.

Consumer Product Applications

Small changes in g-force occur when a hand-held device is tilted. These changes are detected by an accelerometer and interpreted as a command. This principle of simple gesture recognition provides for a natural and more engaging user interface.

Motion sensing, by means of MEMS inertial sensors, can be applied to a wide array of consumer products— computer games, cell phones, pagers, PDAs, advanced robotics, laptop computers, computer input devices, camcorders, digital cameras, and after-market SD card accessories.

Game Play — The need for precision, a realistic "feel," and multi-position handling make this potentially one of the largest consumer electronics applications for tilt interface.

Cell Phones — The location of a cell phone can be accomplished by implanting a GPS chip and a MEMS inertial sensor into a phone. A tilt interface allows one-handed operation and can provide motion awareness to the cell phone, enabling power management and advanced user interfaces.

Advanced Robotics — Useful in many industries, advanced robotics requires motion measurement within six degrees- of-freedom, both acceleration and angular rate about three axes. The greater the ability to sense the full motion of the robot and its parts, the better the control over its behavior.

Laptop Computers — Security and disk-drive protection are of utmost concern to users. Accelerometers can be used to detect unwarranted motion, thus triggering an alarm. Likewise, an accelerometer can detect the computer's fall and retract the disc head from the platter to prevent damage to the disk drive.

Computer Input Devices — Input devices, such as a mouse, a joystick, or a touch pad, translate user motion into computer action. Inertial sensors can be used to develop much more sophisticated interfaces, a mouse that moves within three dimensions, and digital pens that use character recognition to translate user writing into digital text and computer commands.

Camcorders and Digital Cameras — Inertial sensors can provide image stabilization and can electronically reduce or remove the unwanted motion introduced by the user.

SD Card Accessory — For PDAs, cell phones, and other mobile devices that have a Secure Digital (SD) card slot with I/O capability. An SD hybrid card containing a very thin Kionix MEMS sensor, interface ASIC, support logic, memory, and firmware can be operated using the appropriate software drivers and application-level software on the host device.

Automotive Applications for Kionix Inertial Sensors

Safety, passenger comfort, and vehicle performance applications are triggering new and tremendous demand for cost effective inertial sensing. Kionix, with its robust technology, is uniquely positioned to respond decisively.

Sensing for Airbag Control — Currently the largest automotive use of MEMS inertial sensors. One or more accelerometers continuously measure vehicle acceleration. Impact beyond a preset threshold triggers a micro-controller that determines if air bag deployment is warranted.

Rollover Detection — These systems combine accelerometers and gyroscopes to read vehicular roll angle and rate. If a vehicle is tipping, side curtain air bags are fired to protect occupants.

Active Suspension — Accelerometers at each wheel and throughout the vehicle continually monitor road conditions, stiffening and softening the suspension for optimal safety and passenger comfort.

Tire Pressure Monitoring — Direct TPM Systems measure tire pressure and send information to a dashboard display. Accelerometers in the tire activate TPM only when the wheel is in motion allowing long life on a single battery.

Vehicle Stability Control — Expanding on the base of antilock braking (ABS), VSC systems allow drivers to regain control of a skidding vehicle. Low-g accelerometers measure lateral slide and a gyroscope measures yaw rate.

Antitheft Systems — Most stolen vehicles are simply towed away. In response, automakers are incorporating tilt-sensing accelerometers into their anti-theft systems.

Electronic Parking Brake — Low-g accelerometers are used to measure vehicle inclination in order to apply a desired amount of braking force.

Vehicle Navigation Systems — Navigation systems rely on a compass and Global Positioning System (GPS) to establish initial direction. When the GPS signal is blocked, MEMS inertial sensors provide dead reckoning of the vehicle's travels until GPS is reacquired.

Adaptive Cruise Control — Data from a variety of environmental sensors creates a virtual depiction of the traffic scene surrounding a vehicle. The ACC uses gyroscopes to measure yaw rate, steering wheel angle, and wheel speeds. The data is then applied to a reference vehicle for safe distance monitoring.

The Sensor Cluster — A six degree-of-freedom inertial measurement unit (IMU) is positioned near the center of the vehicle to feed information to all inertial accessory systems — antitheft, VSC, navigation, and the like.

Sensor Operation

Kionix inertial sensors operate on the principle of differential capacitance. Each axis (X, Y, or Z) is equipped with a sense element that moves in relationship to a fixed base within the part. When the sense element moves along the axis, its distance from the fixed element changes and a small shifting electrical capacitance occurs. This shift, the resulting difference between the sensor chip and the fixed base, is measured by a Kionix Application- Specific Integrated Circuit (ASIC), and turned into an analog or digital signal proportional to acceleration or angular rate.

Packaging

Kionix sensor solutions are currently available in three advanced packages: The traditional over-molded SOIC package offers good performance at low cost. Higher performance applications utilize an open-cavity package, a hollow plastic form in which the sensor die is placed and capped for full protection. Kionix engineers have developed a chip-scale package the 14-land 5x5x1.8mm Dual Flat No-lead (DFN) which houses the Kionix high-performance tri-axis accelerometer.

In development now are groundbreaking new package concepts that will set a new standard for the MEMS industry.

Contact

For any further information on the Kionix range of accelerometers please contact sales@willow.co.uk or Tel. + 44 (0) 1342 835234 / Fax. + 44 (0) 1342 834306