ADXL320EB Analog Devices Inc, ADXL320EB Datasheet - Page 11

• Manufacturer Part Number: ADXL320EB
• Description: BOARD EVAL FOR ADXL320
• Manufacturer: Analog Devices Inc
• Series: iMEMS®r

Specifications of ADXL320EB

• Sensor Type: Accelerometer, 2 Axis
• Sensing Range: ±5g
• Interface: Analog
• Sensitivity: 174mV/g
• Voltage - Supply: 2.4 V ~ 5.25 V
• Embedded: No
• Utilized Ic / Part: ADXL320
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

THEORY OF OPERATION
The ADXL320 is a complete acceleration measurement system
on a single monolithic IC. The ADXL320 has a measurement
range of ±5 g. 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 that are proportional to acceleration. The
accelerometer measures static acceleration forces, such as
gravity, which allows it to be used as a tilt sensor.
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 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.
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The demodulator’s 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.
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 neither
quantization error nor nonmonotonic behavior, and
temperature hysteresis is very low (typically less than 3 mg over
the −20°C to +70°C temperature range).
Figure 10 shows the zero g output performance of eight parts
(X- and Y-axis) over a −20°C to +70°C temperature range.
Figure 13 demonstrates the typical sensitivity shift over
temperature for supply voltages of 3 V. This is typically better
than ±1% over the −20°C to +70°C temperature range.
ADXL320