MMA2201D Freescale Semiconductor, MMA2201D Datasheet - Page 4

• Manufacturer Part Number: MMA2201D
• Description: SENS ACCEL X-AXIS +-38G 16-SOIC
• Manufacturer: Freescale Semiconductor
• Series: MMAr

Specifications of MMA2201D

• Axis: X or Y
• Acceleration Range: ±45g
• Sensitivity: 50mV/g
• Voltage - Supply: 4.75 V ~ 5.25 V
• Output Type: Analog
• Bandwidth: 400Hz
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.50mm Width)
• Sensing Axis: X
• Acceleration: 40 g
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Interface: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: MMA2201DTR; MMA2201DTR

PRINCIPLE OF OPERATION
integrated-circuit accelerometer.
sensing cell (g-cell) and a CMOS signal conditioning ASIC
contained in a single integrated circuit package. The sensing
element is sealed hermetically at the wafer level using a bulk
micromachined “cap'' wafer.
semiconductor materials (polysilicon) using semiconductor
processes (masking and etching). It can be modeled as a set of
beams attached to a movable central mass that move between
fixed beans. The movable beams can be deflected from their
rest position by subjecting the system to an acceleration
(Figure 2).
distance from them to the fixed beams on one side will increase
by the same amount that the distance to the fixed beams on the
other side decreases. The change in distance is a measure of
acceleration.
(Figure 2). As the center plate moves with acceleration, the
distance between the beams change and each capacitor's
value will change, (C = NAε/D). Where A is the area of the
facing side of the beam, ε is the dielectric constant, and D is the
distance between the beams, and N is the number of beams.
measure the g-cell capacitors and extract the acceleration data
from the difference between the two capacitors. The ASIC also
signal conditions and filters (switched capacitor) the signal,
providing a high level output voltage that is ratiometric and
proportional to acceleration.
Figure 2. Simplified Transducer Physical Model
SPECIAL FEATURES
Filtering
switched capacitor filter. A Bessel implementation is used
because it provides a maximally flat delay response (linear
phase) thus preserving pulse shape integrity. Because the filter
is realized using switched capacitor techniques, there is no
requirement for external passive components (resistors and
capacitors) to set the cut-off frequency.
MMA2201D
4
The Motorola accelerometer is a surface-micromachined
The device consists of a surface micromachined capacitive
The g-cell is a mechanical structure formed from
When the beams attached to the center mass move, the
The g-cell beams form two back-to-back capacitors
The CMOS ASIC uses switched capacitor techniques to
The Motorola accelerometers contain an onboard 4-pole
Acceleration
Freescale Semiconductor, Inc.
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Self-Test
verification of the mechanical and electrical integrity of the
accelerometer at any time before or after installation. This
feature is critical in applications such as automotive airbag
systems where system integrity must be ensured over the life of
the vehicle. A fourth “plate'' is used in the g-cell as a self-test
plate. When the user applies a logic high input to the self-test
pin, a calibrated potential is applied across the self-test plate
and the moveable plate. The resulting electrostatic force
(Fe =
resultant deflection is measured by the accelerometer's control
ASIC and a proportional output voltage results. This procedure
assures that both the mechanical (g-cell) and electronic
sections of the accelerometer are functioning.
Ratiometricity
and sensitivity will scale linearly with applied supply voltage.
That is, as you increase supply voltage the sensitivity and offset
increase linearly; as supply voltage decreases, offset and
sensitivity decrease linearly. This is a key feature when
interfacing to a microcontroller or an A/D converter because it
provides system level cancellation of supply induced errors in
the analog to digital conversion process.
Status
a fault latch. The Status pin is an output from the fault latch,
OR'd with self-test, and is set high whenever one (or more) of
the following events occur:
•
•
•
input pin, unless one (or more) of the fault conditions continues
to exist.
The sensor provides a self-test feature that allows the
Ratiometricity simply means that the output offset voltage
Motorola accelerometers include fault detection circuitry and
The fault latch can be reset by a falling edge on the self-test
Supply voltage falls below the Low Voltage Detect (LVD)
voltage threshold
Clock oscillator falls below the clock monitor minimum
frequency
Parity of the EPROM bits becomes odd in number.
1
/
2
AV
2
/d
2
) causes the center plate to deflect. The
Motorola Sensor Device Data