Datasheet ADXL206 (Analog Devices) - 10

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Data Sheet ADXL206 THEORY OF OPERATION
The ADXL206 is a complete acceleration measurement system The output of the demodulator is amplified and brought off chip on a single, monolithic IC. The part contains a polysilicon, surface- through a 32 kΩ resistor. At this point, the user can set the signal micromachined sensor and signal conditioning circuitry to imple- bandwidth of the device by adding a capacitor. This filtering ment an open-loop acceleration measurement architecture. The improves measurement resolution and helps prevent aliasing. output signals are analog voltages proportional to acceleration.
PERFORMANCE
The ADXL206 is capable of measuring both positive and negative accelerations to at least ±5 g. The accelerometer can measure Rather than using additional temperature compensation circuitry, static acceleration forces such as gravity, allowing it to be used innovative design techniques have been used to ensure that high as a tilt sensor. performance is built in. As a result, there is essentially no quantiza- tion error or nonmonotonic behavior, and temperature hysteresis The sensor is a surface-micromachined, polysilicon structure is very low (typically less than 2 mg over the −40°C to +175°C built on top of the silicon wafer. Polysilicon springs suspend the temperature range). structure over the surface of the wafer and provide resistance against acceleration forces. Deflection of the structure is measured Figure 12 shows the 0 g output performance of eight parts over using a differential capacitor that consists of independent fixed the −40°C to +175°C temperature range. plates and plates attached to the moving mass. The fixed plates Figure 11 and Figure 14 show the typical sensitivity shift over are driven by 180° out-of-phase square waves. Acceleration deflects temperature for VS = 5 V. Sensitivity stability is optimized for the beam and unbalances the differential capacitor, resulting in VS = 5 V, but it is very good over the full supply voltage range. an output square wave whose amplitude is proportional to accel- eration. Phase-sensitive demodulation techniques are then used to rectify the signal and determine the direction of the acceleration. Rev. B | Page 9 of 12 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION PERFORMANCE APPLICATIONS INFORMATION POWER SUPPLY DECOUPLING SETTING THE BANDWIDTH USING CX AND CY SELF-TEST DESIGN TRADE-OFFS FOR SELECTING FILTER CHARACTERISTICS: NOISE/BANDWIDTH TRADE-OFF USING THE ADXL206 WITH OPERATING VOLTAGES OTHER THAN 5 V USING THE ADXL206 AS A DUAL-AXIS TILT SENSOR Dual-Axis Tilt Sensor: Converting Acceleration to Tilt OUTLINE DIMENSIONS ORDERING GUIDE