ADXL377 データシートの表示（PDF） - Analog Devices

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ADXL377

Small, Low Power, 3-Axis ±200 g Accelerometer

Analog Devices 

ADXL377

THEORY OF OPERATION

The ADXL377 is a complete 3-axis acceleration measurement

system with a typical measurement range of ±200 g. The ADXL377

contains a polysilicon, surface-micromachined sensor and signal

conditioning circuitry to implement an open-loop acceleration

measurement architecture. The output signals are analog voltages

that are proportional to acceleration. The accelerometer can mea-

sure the static acceleration of gravity in tilt-sensing applications,

as well as dynamic acceleration resulting from motion, shock,

or vibration.

The sensor is a polysilicon, surface-micromachined structure

built on top of a silicon wafer. Polysilicon springs suspend the

structure over the surface of the wafer and provide resistance

against acceleration forces. Deflection of the structure is mea-

sured using a differential capacitor that consists of independent

fixed plates and plates attached to the moving mass. The fixed

plates are driven by 180° out-of-phase square waves. Acceleration

deflects the moving mass and unbalances the differential capacitor,

resulting in a sensor output whose amplitude is proportional to

acceleration. Phase-sensitive demodulation techniques are then

used to determine the magnitude and direction of the acceleration.

Data Sheet

The demodulator output is amplified and brought off chip through

a 32 kΩ resistor. The user then sets the signal bandwidth of the

device by adding a capacitor. This filtering improves measurement

resolution and helps prevent aliasing.

MECHANICAL SENSOR

The ADXL377 uses a single structure for sensing the accelera-

tion in the x-axis, y-axis, and z-axis. As a result, the three sense

directions are highly orthogonal with little cross-axis sensitivity.

Mechanical misalignment of the sensor die to the package or

misalignment of the package to the PCB is the chief source of

cross-axis sensitivity. Mechanical misalignment can be calibrated

at the system level.

PERFORMANCE

Rather than using additional temperature compensation circuitry,

the ADXL377 uses innovative design techniques to ensure high

performance. As a result, there is neither quantization error nor

nonmonotonic behavior, and temperature hysteresis is very low.

Rev. 0 | Page 8 of 12

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