MOTOROLA MMA2201D User Manual

MOTOROLA

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SEMICONDUCTOR TECHNICAL DATA

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

• 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 W afer Level for Superior Reliability

• Robust Design, High Shocks Survivability

T ypical 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

Order this document

by MMA2201D/D

MMA2201D

MMA2201D: X AXIS SENSITIVITY

MICROMACHINED

ACCELEROMETER

±40g

16

9

1

8

16 LEAD SOIC

CASE 475–01

SIMPLIFIED ACCELEROMETER FUNCTIONAL BLOCK DIAGRAM

G–CELL

SENSOR

V

ST

REV 0

 Motorola, Inc. 2000

SELF–TEST

Figure 1. Simplified Accelerometer Functional Block Diagram

INTEGRATOR GAIN FILTER

CONTROL LOGIC &

EPROM TRIM CIRCUITS

STATUS

OSCILLATOR

TEMP

COMP

CLOCK GEN.

V

V

V

DD

OUT

SS

1Motorola Sensor Device Data

MMA2201D

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MAXIMUM RATINGS

Powered Acceleration (all axes) G
Unpowered Acceleration (all axes) G
Supply Voltage V
Drop Test
Storage Temperature Range T

NOTES:

(1)

1. Dropped onto concrete surface from any axis.

(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)

Rating Symbol Value Unit

ELECTRO ST ATIC 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

500 g

2000 g

–0.3 to +7.0 V

1.2 m

–40 to +105 °C

D

pd
upd
DD

drop

stg

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.

2 Motorola Sensor Device Data

MMA2201D

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OPERATING CHARACTERISTICS

DD

(1)

5.00

5.0
—
38

2.5

0.50 V
50
10

400

—

—

110

2.0

12
—
—

*

2.0

—
—

0.2
—
—

300

—
10

)

110

DD

5.25

6.0

+85

—

2.7

0.56 V

DD

52.5

10.7
440

+1.0

2.8
—
—

14

0.3 x V

DD

V

DD

*

300

10

0.4
—

—

VDD *0.3

100

—

5.0
—

V

mA

°C

g

V
V

mV/g

mV/g/V

Hz

% FSO

mVrms

µV/(Hz

mVpk

g
V
V

µA

ms

V
V

ms

V

pF

Ω

% FSO

kHz

(Unless otherwise noted: –40°C v TA v +85°C, 4.75 v VDD v 5.25, Acceleration = 0g, Loaded output

Characteristic

Operating Range

Supply Voltage
Supply Current
Operating Temperature Range
Acceleration Range

Output Signal

Zero g (VDD = 5.0 V)
Zero g
Sensitivity (TA = 25°C, VDD = 5.0 V)
Sensitivity
Bandwidth Response
Nonlinearity

Noise

RMS (.01–1 kHz)
Power Spectral Density
Clock Noise (without RC load on output)

Self–Test

Output Response
Input Low
Input High
Input Loading
Response Time

(12)(13)

Status

Output Low (I

Output High (I
Minimum Supply Voltage (LVD Trip) V
Clock Monitor Fail Detection Frequency f
Output Stage Performance

Electrical Saturation Recovery Time

Full Scale Output Range (I

Capacitive Load Drive

Output Impedance
Mechanical Characteristics

Transverse Sensitivity

Package Resonance

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.

(2)
(3)

(7)

(8)

load

load

(4)

= 100 µA)

= 100 µA)

(10)

(11)

OUT

(5)

(6)

(9)

= 200 µA)

Symbol Min Typ Max Unit

V

DD

I

DD
T

A

g

FS

V

OFF

V

OFF,V

S

S

V

f

–3dB

NL

OUT

n

RMS

n

PSD

n

CLK

g

ST

V

IL

V

IH

I

IN

t

ST

V

OL

V

OH
LVD
min

t

DELAY

V

FSO

C

Z

O

V

ZX,YX

f

PKG

L

4.75

4.0

*

40

—

2.3

0.44 V

DD

47.5

9.3

360

*

1.0

—
—
—

10

V

SS

0.7 x V

*

30

—

—

VDD *.8

2.7 3.25 4.0 V

150 — 400 kHz

—

0.3
—
—

—
—

1/2

)

3Motorola Sensor Device Data

MMA2201D

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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 .

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.

BASIC CONNECTIONS

Pinout Description

V

N/C
N/C
N/C

ST

OUT

N/C

V

SS

V

DD

1
2
3
4
5
6
7
8

4 Motorola Sensor Device Data

16
15
14
13
12
11
10

N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C

9

Pin No. Pin Name Description

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MMA2201D

PCB Layout

1 thru 3 — No internal connection. Leave

4 ST Logic input pin used to initiate

5 V

6 — No internal connection. Leave

7 V
8 V

9 thru 13 Trim pins Used for factory trim. Leave

14 thru 16 — No internal connection. Leave

V

DD

LOGIC

INPUT

C1

0.1 µF

OUT

SS
DD

4
8

7

ST
V

V

DD

SS

unconnected.

self–test.

Output voltage of the accelerome-

ter.

unconnected.
The power supply ground.
The power supply input.

unconnected.

unconnected.

V

OUT

6

R1

1 kΩ

5

C2

0.01 µF

MMA2201D

STATUS

OUTPUT
SIGNAL

Figure 4. SOIC Accelerometer with Recommended

Connection Diagram

P1STATUS

MICROCONTROLLER

0.1 µF

P0

A/D IN

V

RH

V

SS

C

0.1 µF

V

DD

ST

V

OUT

V

SS

ACCELEROMETER

V

DD

1 kΩ

C

0.1 µF

POWER SUPPLY

R

C

0.01 µF

C

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.

5Motorola Sensor Device Data

MMA2201D

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Positive Acceleration Sensing Direction

AXIS

ORIENTATION

–X +X

(ACCELERATION

FORCE

VECTOR)

87654321

10 11 12 13 14 15 16

9

* When positioned as shown, the Earth’s gravity will result in a positive 1g output

N/C
N/C
N/C

SELF TEST

X

OUT

N/C

V

SS

V

DD

N/C pins are recommended to be left FLOATING

Direction of Earth’s gravity field.*

1
2
3
4
5
6
7
8

16–Pin SOIC Package

16
15
14
13
12

11

10

N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C

9

ORDERING INFORMATION

Device Temperature Range Case No. Package

MMA2201D

*

40 to +85°C Case 475–01 SOIC–16

6 Motorola Sensor Device Data