MOTOROLA MMA1213DR2

Freescale Semiconductor, Inc.
MOTOROLA
Order Number: MMA1213D
Rev. 0, 06/2004
SEMICONDUCTOR TECHNICAL DATA
Surface Mount
Micromachined Accelerometer
MMA1213D
Freescale Semiconductor, Inc...
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.
MMA1213D: Z AXIS SENSITIVITY
MICROMACHINED
ACCELEROMETER
±50g
Features
• Integral Signal Conditioning
• Linear Output
• Ratiometric Performance
• 4th Order Bessel Filter Preserves Pulse Shape Integrity
• Calibrated Self-test
• Low Voltage Detect, Clock Monitor, and EPROM Parity Check Status
• Transducer Hermetically Sealed at Wafer Level for Superior Reliability
• Robust Design, High Shocks Survivability
Typical Applications
• Vibration Monitoring and Recording
• Impact Monitoring
16 LEAD SOIC
CASE 475–01
ORDERING INFORMATION
Device
Temperature
Range
Package
PIN ASSIGNMENT
MMA1213D
– 40 to +125°C
SOIC-16
MMA1213DR2
– 40 to +125°C
SOIC-16, Tape & Reel
N/C
N/C
N/C
ST
VOUT
STATUS
VSS
VDD
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
VDD
G-Cell
Sensor
ST
Self-test
Integrator
Gain
Control Logic &
EPROM
Trim Circuits
Filter
Temp
Comp
Oscillator
Clock
Gen.
Status
Figure 1. Simplified Accelerometer Functional Block Diagram
REV 0
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VOUT
VSS
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
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Maximum Ratings
(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating
Symbol
Value
Unit
Powered Acceleration (all axes)
Gpd
1500
g
Unpowered Acceleration (all axes)
Gupd
2000
g
Supply Voltage
VDD
–0.3 to +7.0
V
Drop Test (1)
Ddrop
1.2
m
Tstg
–40 to +125
°C
Storage Temperature Range
NOTES:
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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 2000 volts
can accumulate on the human body or associated test
equipment. A charge of this magnitude can alter the
MMA1213D
2
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.
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Operating Characteristics
(Unless otherwise noted: –40°C ≤ TA ≤ +105°C, 4.75 ≤ VDD ≤ 5.25, Acceleration = 0g, Loaded output.(1))
Characteristic
Symbol
Min
Typ
Max
Unit
VDD
IDD
TA
gFS
4.75
3.0
–40
—
5.00
—
—
56.3
5.25
6.0
+125
—
V
mA
°C
g
VOFF
VOFF,V
S
SV
f–3dB
NLOUT
2.35
0.46 VDD
38
7.44
360
–1.0
2.5
0.50 VDD
40
8
400
—
2.65
0.54 VDD
42
8.56
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
24
VSS
0.7 × VDD
–30
—
30
—
—
–100
2.0
36
0.3 × VDD
VDD
–260
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
—
—
—
Minimum Supply Voltage (LVD Trip)
VLVD
2.7
3.25
4.0
V
fmin
50
—
260
kHz
Output Stage Performance
Electrical Saturation Recovery Time(9)
Full Scale Output Range (IOUT = 200 µA)
Capacitive Load Drive(10)
Output Impedence
tDELAY
VFSO
CL
ZO
—
–0.25
—
—
0.2
—
—
300
—
VDD –0.25
100
—
ms
V
pF
Ω
Mechanical Characteristics
Transverse Sensitivity(11)
Package Resonance
VXZ,YZ
fPKG
—
—
—
10
5.0
—
% FSO
kHz
(2)
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Operating Range
Supply Voltage (3)
Supply Current
Operating Temperature Range
Acceleration Range
Output Signal
Zero g (TA = 25°C, VDD = 5.0 V)(4)
Zero g
Sensitivity (TA = 25°C, VDD = 5.0 V)(5)
Sensitivity
Bandwidth Response
Nonlinearity
Noise
RMS (0.1-1 kHz)
Power Spectral Density
Clock Noise (without RC load on output)(6)
Clock Monitor Fail Detection Frequency
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, as a means to check the connectivity of the self-test and Status pins in the application.
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 low if the self-test pin is pulsed with a high input for at least 100 µs, unless a fault condition continues to exist.
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MMA1213D
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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.
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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
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.
Figure 2. Transducer
Physical Model
Figure 3. Equivalent
Circuit Model
SPECIAL FEATURES
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.
MMA1213D
4
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BASIC CONNECTIONS
Pinout Description
Status
STATUS
VSS
VDD
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16
15
14
13
12
11
10
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
Accelerometer
1
2
3
4
5
6
7
8
1 thru 3
—
Leave unconnected.
4
ST
Logic input pin used to initiate
self-test.
5
VOUT
6
STATUS
Logic output pin to indicate
fault.
7
VSS
The power supply ground.
8
VDD
The power supply input.
9 thru 13
Trim pins
14 thru 16
—
Logic
Input
Description
Output voltage of the
accelerometer.
Used for factory trim. Leave
unconnected.
No internal connection. Leave
unconnected.
8 VDD
C1
0.1 µF
7 VSS
6
VOUT 5
R1
1 kΩ
VSS
P0
A/D In
R
1 kΩ
C 0.01 µF
C 0.1 µF
VSS
C 0.1 µF
VDD
VRH
C 0.1 µF
Pin Name
MMA1213D
4 ST
VOUT
VDD
Pin No.
VDD
ST
Micorocontroller
N/C
N/C
N/C
ST
VOUT
P1
Status
Output
Signal
C2
0.01 µF
Power Supply
Figure 5. Recommended 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.
Figure 4. Accelerometer with Recommended
Connection Diagram
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Dynamic Acceleration Sensing Direction
+Z
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Acceleration of the package in the
+Z direction (center plate moves
in the −Z direction) will result in an
increase in the output.
−Z
Activation of Self test moves
the center plate in the −Z
direction, resulting in an
increase in the output.
Side View
Static Acceleration Sensing Direction
Direction of Earth's gravity field.*
Side View
* When positioned as shown, the Earth's gravity will result in a positive 1g output.
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Motorola Sensor Device Data
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PACKAGE DIMENSIONS
A
A
G/2
2 PLACES, 16 TIPS
G
16
0.15 T A B
B
P
1
B
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NOTES:
1. ALL DIMENSIONS ARE IN MILLIMETERS.
2. INTERPRET DIMENSIONS AND TOLERANCES
PER ASME Y14.5M, 1994.
3. DIMENSIONS "A" AND "B" DO NOT INCLUDE
MOLD FLASH OR PROTRUSIONS. MOLD FLASH
OR PROTRUSIONS SHALL NOT EXCEED 0.15
PER SIDE.
4. DIMENSION "D" DOES NOT INCLUDE DAMBAR
PROTRUSION. PROTRUSIONS SHALL NOT
CAUSE THE LEAD WIDTH TO EXCEED 0.75
9
8
16X
D
0.13
M
T A B
R
J
C
0.1
K
T
X 45˚
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
SEATING
PLANE
CASE 475-01
ISSUE B
CASE16
475-01
LEAD SOIC
ISSUE B
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
Surface mount board layout is a critical portion of the total
design. The footprint for the surface mount packages must be
the correct size to ensure proper solder connection interface
between the board and the package. With the correct footprint,
0.380 in.
9.65 mm
the packages will self-align when subjected to a solder reflow
process. It is always recommended to design boards with a
solder mask layer to avoid bridging and shorting between solder
pads.
0.050 in.
1.27 mm
0.024 in.
0.610 mm
0.080 in.
2.03 mm
Figure 6. Footprint SOIC-16 (Case 475-01)
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Information in this document is provided solely to enable system and software implementers to use Motorola products. There are no express or implied
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Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee
regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product
or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. “Typical” parameters which may be
provided in Motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating
parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. Motorola does not convey any license
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© Motorola, Inc. 2004
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MMA1213D