ADXL204 Просмотр технического описания (PDF) - Analog Devices
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ADXL204 Datasheet PDF : 12 Pages
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THEORY OF OPERATION
PIN 8
XOUT = 1.03V
YOUT = 1.65V
ADXL204
PIN 8
XOUT = 1.65V
YOUT = 2.27V
TOP VIEW
(Not to Scale)
PIN 8
XOUT = 1.65V
YOUT = 1.03V
PIN 8
XOUT = 2.27V
YOUT = 1.65V
XOUT = 1.65V
YOUT = 1.65V
EARTH'S SURFACE
Figure 22. Output Response vs. Orientation
The ADXL204 is a complete acceleration measurement system on
a single monolithic IC. The ADXL204 is a dual-axis accelerometer.
It contains a polysilicon surface-micromachined sensor and
signal conditioning circuitry to implement an open-loop
acceleration measurement architecture. The output signals are
analog voltages proportional to acceleration. The ADXL204 is
capable of measuring both positive and negative accelerations to
at least ±1.7 g. The accelerometer can measure static acceleration
forces, such as gravity, allowing it to be used as a tilt sensor.
The sensor is a surface-micromachined polysilicon structure
built on top of the silicon wafer. Polysilicon springs suspend the
structure over the surface of the wafer and provide a resistance
against acceleration forces. Deflection of the structure is measured
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 beam and unbalances the differential capacitor,
resulting in an output square wave whose amplitude is
proportional to acceleration. Phase-sensitive demodulation
techniques are then used to rectify the signal and determine
the direction of the acceleration.
The output of the demodulator is amplified and brought off-
chip through a 32 kΩ resistor. At this point, the user can set the
signal bandwidth of the device by adding a capacitor. This filtering
improves measurement resolution and helps prevent aliasing.
PERFORMANCE
Rather than using additional temperature compensation
circuitry, innovative design techniques have been used to ensure
high performance is built in. As a result, there is essentially no
quantization error or nonmonotonic behavior, and temperature
hysteresis is very low, typically less than 10 mg over the –40°C
to +125°C temperature range.
Figure 10 shows the zero g output performance of eight parts
(X-axis and Y-axis) over a –40°C to +125°C temperature range.
Figure 13 demonstrates the typical sensitivity shift over tem-
perature for VS = 3.3 V. Sensitivity stability is typically better
than ±1% over temperature.
Rev. A | Page 9 of 12
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