ADXL204EB Analog Devices Inc, ADXL204EB Datasheet - Page 9

• Manufacturer Part Number: ADXL204EB
• Description: EVAL BOARD
• Manufacturer: Analog Devices Inc
• Series: iMEMS®r

Specifications of ADXL204EB

• Silicon Manufacturer: Analog Devices
• Application Sub Type: Accelerometer - Dual-Axis
• Kit Application Type: Sensing - Motion / Vibration / Shock
• Silicon Core Number: ADXL204
• Silicon Family Name: IMEMS
• Sensor Type: Accelerometer, 2 Axis
• Sensing Range: ±1.7g
• Interface: Analog
• Sensitivity: 620mV/g
• Voltage - Supply: 3 V ~ 6 V
• Embedded: No
• Utilized Ic / Part: ADXL204
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

THEORY OF OPERATION
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.
X
Y
OUT
OUT
= 1.65V
= 2.27V
PIN 8
Figure 22. Output Response vs. Orientation
(Not to Scale)
X
Y
X
Y
TOP VIEW
OUT
OUT
OUT
OUT
Rev. A | Page 9 of 12
PIN 8
PIN 8
= 1.03V
= 1.65V
= 2.27V
= 1.65V
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 V
than ±1% over temperature.
PIN 8
X
Y
EARTH'S SURFACE
OUT
OUT
= 1.65V
= 1.03V
S
X
Y
= 3.3 V. Sensitivity stability is typically better
OUT
OUT
= 1.65V
= 1.65V
ADXL204