MOTOROLA MMA2201D Surface mount micromachined accelerometer Datasheet

MOTOROLA
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by MMA2201D/D
SEMICONDUCTOR TECHNICAL DATA
MMA2201D
Surface Mount
Micromachined Accelerometer
The MMA series of silicon capacitive, micromachined accelerometers
features signal conditioning, a 4–pole low pass filter and temperature
compensation. Zero–g offset full scale span and filter cut–off are factory set and
require no external devices. A full system self–test capability verifies system
functionality.
Features
MMA2201D: X AXIS SENSITIVITY
MICROMACHINED
ACCELEROMETER
± 40g
• Integral Signal Conditioning
• Linear Output
• Ratiometric Performance
16
• 4th Order Bessel Filter Preserves Pulse Shape Integrity
9
• Calibrated Self–test
1
• Low Voltage Detect, Clock Monitor, and EPROM Parity Check Status
8
• Transducer Hermetically Sealed at Wafer Level for Superior Reliability
16 LEAD SOIC
CASE 475–01
• Robust Design, High Shocks Survivability
Typical Applications
• Vibration Monitoring and Recording
• Appliance Control
• Mechanical Bearing Monitoring
• Computer Hard Drive Protection
• Computer Mouse and Joysticks
• Virtual Reality Input Devices
• Sports Diagnostic Devices and Systems
SIMPLIFIED ACCELEROMETER FUNCTIONAL BLOCK DIAGRAM
VDD
G–CELL
SENSOR
VST
SELF–TEST
INTEGRATOR
GAIN
CONTROL LOGIC &
EPROM TRIM CIRCUITS
FILTER
OSCILLATOR
TEMP
COMP
VOUT
CLOCK GEN.
VSS
STATUS
Figure 1. Simplified Accelerometer Functional Block Diagram
REV 0
Motorola Sensor Device Data
 Motorola, Inc. 2000
1
MMA2201D
MAXIMUM RATINGS (Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Symbol
Value
Unit
Powered Acceleration (all axes)
Rating
Gpd
500
g
Unpowered Acceleration (all axes)
Gupd
2000
g
Supply Voltage
VDD
–0.3 to +7.0
V
Ddrop
1.2
m
Tstg
– 40 to +105
°C
Drop Test(1)
Storage Temperature Range
NOTES:
1. Dropped onto concrete surface from any axis.
ELECTRO STATIC DISCHARGE (ESD)
WARNING: This device is sensitive to electrostatic
discharge.
Although the Motorola accelerometers contain internal
2kV ESD protection circuitry, extra precaution must be taken
by the user to protect the chip from ESD. A charge of over
2
2000 volts can accumulate on the human body or associated
test equipment. A charge of this magnitude can alter the performance or cause failure of the chip. When handling the
accelerometer, proper ESD precautions should be followed
to avoid exposing the device to discharges which may be
detrimental to its performance.
Motorola Sensor Device Data
MMA2201D
OPERATING CHARACTERISTICS
(Unless otherwise noted: –40°C
v TA v +85°C, 4.75 v VDD v 5.25, Acceleration = 0g, Loaded output(1))
Characteristic
Symbol
Min
Typ
Max
Unit
VDD
IDD
TA
gFS
4.75
4.0
40
—
5.00
5.0
—
38
5.25
6.0
+85
—
V
mA
°C
g
VOFF
VOFF,V
S
SV
f –3dB
NLOUT
2.3
0.44 VDD
47.5
9.3
360
1.0
2.5
0.50 VDD
50
10
400
—
2.7
0.56 VDD
52.5
10.7
440
+1.0
V
V
mV/g
mV/g/V
Hz
% FSO
nRMS
nPSD
nCLK
—
—
—
—
110
2.0
2.8
—
—
mVrms
µV/(Hz1/2)
mVpk
Self–Test
Output Response
Input Low
Input High
Input Loading(7)
Response Time(8)
gST
VIL
VIH
IIN
tST
10
VSS
0.7 x VDD
30
—
14
0.3 x VDD
VDD
300
10
g
V
V
µA
ms
Status(12)(13)
Output Low (Iload = 100 µA)
Output High (Iload = 100 µA)
VOL
VOH
—
VDD .8
—
—
0.4
—
V
V
Minimum Supply Voltage (LVD Trip)
VLVD
2.7
3.25
4.0
V
fmin
150
—
400
kHz
Output Stage Performance
Electrical Saturation Recovery Time(9)
Full Scale Output Range (IOUT = 200 µA)
Capacitive Load Drive(10)
Output Impedance
tDELAY
VFSO
CL
ZO
—
0.3
—
—
0.2
—
—
300
—
VDD 0.3
100
—
ms
V
pF
Ω
Mechanical Characteristics
Transverse Sensitivity(11)
Package Resonance
VZX,YX
fPKG
—
—
—
10
5.0
—
% FSO
kHz
Operating Range(2)
Supply Voltage(3)
Supply Current
Operating Temperature Range
Acceleration Range
Output Signal
Zero g (VDD = 5.0 V)(4)
Zero g
Sensitivity (TA = 25°C, VDD = 5.0 V)(5)
Sensitivity
Bandwidth Response
Nonlinearity
Noise
RMS (.01–1 kHz)
Power Spectral Density
Clock Noise (without RC load on output)(6)
Clock Monitor Fail Detection Frequency
*
*
*
*
12
—
—
110
2.0
*
*
*
NOTES:
1. For a loaded output the measurements are observed after an RC filter consisting of a 1 kΩ resistor and a 0.01 µF capacitor to ground.
2. These limits define the range of operation for which the part will meet specification.
3. Within the supply range of 4.75 and 5.25 volts, the device operates as a fully calibrated linear accelerometer. Beyond these supply limits
the device may operate as a linear device but is not guaranteed to be in calibration.
4. The device can measure both + and acceleration. With no input acceleration the output is at midsupply. For positive acceleration the output
will increase above VDD/2 and for negative acceleration the output will decrease below VDD/2.
5. The device is calibrated at 20g.
6. At clock frequency
70 kHz.
7. The digital input pin has an internal pull–down current source to prevent inadvertent self test initiation due to external board level leakages.
8. Time for the output to reach 90% of its final value after a self–test is initiated.
9. Time for amplifiers to recover after an acceleration signal causing them to saturate.
10. Preserves phase margin (60°) to guarantee output amplifier stability.
11. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity.
12. The Status pin output is not valid following power–up until at least one rising edge has been applied to the self–test pin. The Status pin is
high whenever the self–test input is high.
13. The Status pin output latches high if a Low Voltage Detection or Clock Frequency failure occurs, or the EPROM parity changes to odd. The
Status pin can be reset by a rising edge on self–test, unless a fault condition continues to exist.
*
^
Motorola Sensor Device Data
3
MMA2201D
PRINCIPLE OF OPERATION
The Motorola accelerometer is a surface–micromachined
integrated–circuit accelerometer.
The device consists of a surface micromachined capacitive 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.
The g–cell is a mechanical structure formed from semiconductor materials (polysilicon) using semiconductor processes (masking and etching). It can be modeled as two
stationary plates with a moveable plate in–between. The
center plate can be deflected from its rest position by subjecting the system to an acceleration (Figure 2).
When the center plate deflects, the distance from it to one
fixed plate will increase by the same amount that the distance to the other plate decreases. The change in distance is
a measure of acceleration.
The g–cell plates form two back–to–back capacitors
(Figure 3). As the center plate moves with acceleration, the
distance between the plates changes and each capacitor’s
value will change, (C = Aε/D). Where A is the area of the
plate, ε is the dielectric constant, and D is the distance
between the plates.
The CMOS ASIC uses switched capacitor techniques to
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.
Acceleration
Figure 2. Transducer
Physical Model
Self–Test
The sensor provides a self–test feature that allows the
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 = 1/2 AV2/d2) causes the center plate to
deflect. The 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
Ratiometricity simply means that the output offset voltage
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
Motorola accelerometers include fault detection circuitry
and 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:
• 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.
The fault latch can be reset by a rising edge on the self–
test input pin, unless one (or more) of the fault conditions
continues to exist.
BASIC CONNECTIONS
Figure 3. Equivalent
Circuit Model
Pinout Description
SPECIAL FEATURES
N/C
Filtering
The Motorola accelerometers contain an onboard 4–pole
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.
N/C
N/C
4
ST
VOUT
N/C
VSS
VDD
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
N/C
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
Motorola Sensor Device Data
MMA2201D
PCB Layout
1 thru 3
—
No internal connection. Leave
unconnected.
4
ST
Logic input pin used to initiate
self–test.
5
VOUT
6
—
Description
Output voltage of the accelerometer.
No internal connection. Leave
unconnected.
7
VSS
The power supply ground.
8
VDD
The power supply input.
9 thru 13
Trim pins
14 thru 16
—
VDD
No internal connection. Leave
unconnected.
LOGIC
INPUT
6
4 ST
8 VDD
VOUT
C1
0.1 µF
7 VSS
5
STATUS
R1
1 kΩ
OUTPUT
SIGNAL
C2
0.01 µF
Figure 4. SOIC Accelerometer with Recommended
Connection Diagram
Motorola Sensor Device Data
P1
ST
VOUT
VSS
VDD
P0
A/D IN
R
1 kΩ
C 0.01 µF
C 0.1 µF
VRH
C
Used for factory trim. Leave
unconnected.
MMA2201D
STATUS
ACCELEROMETER
Pin Name
MICROCONTROLLER
Pin No.
VSS
C 0.1 µF
VDD
0.1 µF
POWER SUPPLY
Figure 5. Recommend PCB Layout for Interfacing
Accelerometer to Microcontroller
NOTES:
• Use a 0.1 µF capacitor on VDD to decouple the power
source.
• Physical coupling distance of the accelerometer to the
microcontroller should be minimal.
• Place a ground plane beneath the accelerometer to reduce
noise, the ground plane should be attached to all of the
open ended terminals shown in Figure 5.
• Use an RC filter of 1 kΩ and 0.01 µF on the output of the
accelerometer to minimize clock noise (from the switched
capacitor filter circuit).
• PCB layout of power and ground should not couple power
supply noise.
• Accelerometer and microcontroller should not be a high
current path.
• A/D sampling rate and any external power supply switching
frequency should be selected such that they do not interfere with the internal accelerometer sampling frequency.
This will prevent aliasing errors.
5
MMA2201D
Positive Acceleration Sensing Direction
N/C
–X
N/C
N/C
AXIS
ORIENTATION
(ACCELERATION
FORCE
VECTOR)
SELF TEST
XOUT
N/C
+X
VSS
VDD
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
16–Pin SOIC Package
N/C pins are recommended to be left FLOATING
8 7
6
5
4
3
2
1
Direction of Earth’s gravity field.*
9 10 11 12 13 14 15 16
* When positioned as shown, the Earth’s gravity will result in a positive 1g output
ORDERING INFORMATION
Device
MMA2201D
6
Temperature Range
*40 to +85°C
Case No.
Case 475–01
Package
SOIC–16
Motorola Sensor Device Data
MMA2201D
PACKAGE DIMENSIONS
–A–
16
9
P 8 PL
0.13 (0.005)
–B–
1
M
T A
B
M
M
8
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSIONS A AND B DO NOT INCLUDE MOLD
PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER
SIDE.
5. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.13 (0.005) TOTAL IN
EXCESS OF D DIMENSION AT MAXIMUM
MATERIAL CONDITION.
D 16 PL
0.13 (0.005)
M
T A
M
B
M
R
X 45 _
K
J
C
–T–
SEATING
PLANE
K
G
F
M
DIM
A
B
C
D
F
G
J
K
M
P
R
MILLIMETERS
MIN
MAX
10.15
10.45
7.40
7.60
3.30
3.55
0.35
0.49
0.76
1.14
1.27 BSC
0.25
0.32
0.10
0.25
0_
7_
10.16
10.67
0.25
0.75
INCHES
MIN
MAX
0.400
0.411
0.292
0.299
0.130
0.140
0.014
0.019
0.030
0.045
0.050 BSC
0.010
0.012
0.004
0.009
0_
7_
0.400
0.420
0.010
0.029
CASE 475–01
ISSUE A
16 LEAD SOIC
Motorola Sensor Device Data
7
MMA2201D
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guarantee regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the
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and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application
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8
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Motorola Sensor Device Data
MMA2201D/D