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AD22293ZA View Datasheet(PDF) - Analog Devices

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AD22293ZA Datasheet PDF : 16 Pages
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Data Sheet
ADXL103/ADXL203
THEORY OF OPERATION
The ADXL103/ADXL203 are complete acceleration measurement
systems on a single, monolithic IC. The ADXL103 is a single-
axis accelerometer, and the ADXL203 is a dual-axis accelerometer.
Both parts contain a polysilicon surface-micro-machined 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
ADXL103/ADXL203 are capable of measuring both positive
and negative accelerations from ±1.7 g to at least ±18 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 that
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 11 shows the 0 g output performance of eight parts
(x and y axes) over a −40°C to +125°C temperature range.
Figure 13 demonstrates the typical sensitivity shift over
temperature for VS = 5 V. Sensitivity stability is optimized for
VS = 5 V but is still very good over the specified range; it is
typically better than ±1% over temperature at VS = 3 V.
PIN 8
XOUT = –1g
YOUT = 0g
PIN 8
XOUT = 0g
YOUT = +1g
TOP VIEW
(Not to Scale)
PIN 8
XOUT = 0g
YOUT = –1g
PIN 8
XOUT = +1g
YOUT = 0g
XOUT = 0g
YOUT = 0g
EARTH’S SURFACE
Figure 39. Output Response vs. Orientation
Rev. D | Page 13 of 16
 

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