Motorola Sensor Device Data

Micromachined Accelerometer

The XMMA series of silicon capacitive, micromachined accelerometers

features; signal conditioning, a 4pole low pass filter and temperature
compensation. Zerog offset full scale span and filter cutoff are factory set and
require no external devices. A full system selftest capability verifies system
functionality.

The XMMA series of accelerometers is suitable for automotive crash

detection and recording, vibration monitoring, automotive suspension control,
appliance control systems, etc.

Features

Minimum Full Scale Measurement

44g

Calibrated, SelfTest

Integral Signal Conditioning and 4Pole Filter

Linear Output

Robust, High Shock Survivability

Ratiometric

GCell, Hermetically Sealed at Wafer Level

Two Packaging Options Available:

1) Plastic DIP for Z Axis Sensing (XMMA1000P)
2) Wingback for X Axis Sensing (XMMA2000W)

Typical Applications

Automotive Crash Detection and Recording

Automotive Suspension Control

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

GCELL

SENSOR

INTEGRATOR

GAIN

FILTER

TEMP

COMP

SELFTEST

CONTROL LOGIC &

EPROM TRIM CIRCUITS

CLOCK GEN.

OSCILLATOR

VDD

VOUT

VSS

VST

Senseon is a trademark of Motorola, Inc.

Replaces MMA1000P/D

Order this document

by XMMA1000P/D

MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

XMMA1000P

XMMA2000W

DIP PACKAGE

CASE 648C03

XMMA1000P

XMMA1000: Z AXIS SENSITIVITY

XMMA2000: X AXIS SENSITIVITY

MICROMACHINED

ACCELEROMETER

50g

2 3

4 5

6 7

WB PACKAGE

CASE 45603

XMMA2000W

Motorola, Inc. 1997

XMMA1000P XMMA2000W

Motorola Sensor Device Data

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 axis)

Gpd

500

Unpowered Acceleration (all axis)

Gupd

2000

Supply Voltage

VDD

0.3 to +7.0

Drop Test(1)

Ddrop

1.2

Storage Temperature Range

Tstg

40 to +105

OPERATING RANGE

(These limits define the range of operation for which the part will meet specification.)

Characteristic

Symbol

Min

Typ

Max

Unit

Supply Voltage(2)

VDD

4.75

5.0

5.25

Supply Current

IDD

1.0

4.0

5.0

Operating Temperature Range

+85

NOTES:

1. Dropped onto concrete surface from any axis.
2. 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.

ELECTRO STATIC DISCHARGE (ESD)

Due to the technological advancing semiconductor indus-

try, it has now become increasingly important for semicon-
ductor manufacturers, users of semiconductors and other
electronic components to fully understand the nature and
sources of ESD. More importantly, a thorough understanding
of its impact on quality and reliability must be understood.

Whereas 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
Automated Test Equipment (ATE). A charge of this magni-
tude can alter the performance or cause failure of the chip.
When proper ESD precautions are followed the discharges
will not be detrimental to the chips performance.

FREQUENTLY ASKED QUESTIONS

Q. What is the gcell?
A. The gcell is the acceleration transducer within the accel-
erometer device. It is hermetically sealed at the wafer level to
ensure a contaminant free environment, resulting in superior
reliability performance.

Q. What does the output typically interface with?
A. The accelerometer device is designed to interface with an
analog to digital converter available on most microcontrol-
lers. The output has a 2.5 V DC offset, therefore positive and
negative acceleration is measurable.

Q. What is the orientation of the gforce in relation to the
output voltage?
A. The accelerometer responds to g forces perpendicular to
the plane of the package. For acceleration directed onto the
top of the package, the output voltage will increase above the
nominal 2.5 V. For acceleration directed away from the top of
the package, the output will decrease below 2.5 V. Refer to
the "Positive Acceleration Sensing Direction'' diagram on
page 7.

Q. What is the resonant frequency of the gcell?
A. The accelerometer's gcell is overdamped. The first reso-
nant mode of the package is 10 kHz for the DIP and 5 kHz for
the Wingback.

Q. What is ratiometricity?
A. Ratiometricity is the sensors ability to track changes in
supply voltage. This is a key feature when interfacing to a
microcontroller or an A/D converter. Ratiometricity allows for
system level cancellation of supply induced errors in the ana-
log to digital conversion process. Refer to the Special Fea-
tures section under the Principle of Operation for more
information.

Q. Is the accelerometer device sensitive to electrostatic
discharge (ESD)?
A. Yes . . . the SENSEON accelerometer should be handled
like other CMOS technology devices.

Q. Can the gcell part "latch''?
A. No, overrange stops have been designed into the gcell
to prevent latching. (Latching is when the middle plate of the
gcell sticks to either the upper or lower plate.)

XMMA1000P XMMA2000W

Motorola Sensor Device Data

OPERATING CHARACTERISTICS

(Unless otherwise noted: 40

+85

, 4.75

VDD

5.25, Acceleration = 0g, Loaded output(1))

Characteristic

Symbol

Min

Typ

Max

Unit

Sensitivity (TA = 25

C, VDD = 5.0 V)(2)

37.2

42.8

mV/g

Sensitivity(2)

7.36

8.0

8.64

mV/V/g

Zero Accel Output(3) (VDD = 5.0 V)

VOFF

2.2

2.5

2.8

Zero Accel Output

VOFF

0.44 VDD

0.5 VDD

0.56 VDD

Acceleration Range(4)

Noise (10 Hz to 400 Hz)(5)

3.5

mVrms

Clock Noise(6)

VNC

2.0

mVpk

Filter Cut Off Frequency

3dB

360

400

440

SelfTest Output Response

GST

SelfTest Input Low

VIL

1.4

SelfTest Input High

VIH

3.7

SelfTest Input Loading(7)

IIN

120

SelfTest Response Time(8)

tST

2.0

Electrical Saturation Recovery Time(9)

0.2

Full Scale Output Range (IOUT = 200

VFSO

0.3

VDD

0.3

Capacitive Load Drive(10)

100

Output Impedance

300

Nonlinearity

1.0

% FSO

Alignment Error

3.0

degrees

Transverse Sensitivity(11)

3.0

% FSO

Package Resonance (DIP/WB)

10/5

kHz

NOTES:

1. For a loaded output the measurements are observed after an RC filter consisting of a 1 k

resistor and a 0.01

F capacitor to ground.

2. The device is calibrated at 20g.
3. 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.

4. Refer to the Principle of Operation section for a sample g range calculation.
5. Refer to the Principle of Operation section for a sample rms to peak to peak calculation.
6. At clock frequency

65 kHz.

7. The digital input pin has an internal pulldown 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 selftest 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 devices ability to reject an acceleration applied 90

from the true axis of sensitivity.

XMMA1000P XMMA2000W

Motorola Sensor Device Data

Pinout description for the Wingback package:

Pin #

Pin Name

Description

No internal connection, tie to VSS

Logic input pin to initiate self test

VOUT

Output voltage

No internal connection, tie to VSS

VSS

Signal ground

VDD

Supply voltage (5 V)

Wings

Support pins, internally connected to lead frame. Tie to VSS.

Pinout description for the DIP package:

2 3

4 5

6 7

Pin #

Pin Name

Description

No internal connection, tie to VSS

Logic input pin to initiate self test

VOUT

Output voltage

No internal connection, tie to VSS

VSS

Signal ground

VDD

Supply voltage (5 V)

Trim 1

Used for factory trim, tie to VSS

Trim 2

Used for factory trim, tie to VSS

Trim 3

Used for factory trim, MUST tie to VDD

Trim 4

Used for factory trim, tie to VSS

Trim 5

Used for factory trim, tie to VSS

No internal connection, tie to VSS

XMMA1000P XMMA2000W

Motorola Sensor Device Data

PRINCIPLE OF OPERATION

The Motorola accelerometer is a surfacemicromachined

integratedcircuit accelerometer.

The device consists of a surface micromachined capaci-

tive sensing cell (Gcell) 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 GCell is a mechanical structure formed from semi-

conductor materials (polysilicon) using semiconductor pro-
cesses (masking and etching). It consists of two stationary
plates with a moveable plate inbetween. The center plate
can be deflected from its rest position by subjecting the sys-
tem to an acceleration (Figure 1).

When the center plate deflects, the distance from it to one

fixed plate will increase by the same amount that the dis-
tance to the other plate decreases. The change in distance is
a measure of acceleration.

The GCell plates form two backtoback capacitors

(Figure 2). As the center plate moves with acceleration, the
distance between the plates changes and each capacitor's
value will change, (C = A

/D). Where A is the area of the

plate,

is the dielectric constant, and D is the distance

between the plates.

The CMOS ASIC uses switched capacitor techniques to

measure the GCell 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 ratio-
metric and proportional to acceleration.

Acceleration

Figure 1.

Figure 2.

SPECIAL FEATURES

Filtering

The Motorola accelerometers contain an onboard 4pole

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 fil-
ter is realized using switched capacitor techniques, there is
no requirement for external passive components (resistors
and capacitors) to set the cutoff frequency.

Noise Calculation

The noise for the Motorola accelerometer is specified as

an rms value which is a statistical value of a gaussian noise
source. To convert the rms values to a peak to peak value at
a particular confidence level refer to Table 1. A sample cal-
culation at a 99.9% confidence level is shown.

Table 1.

Nominal Peak to Peak Value

% Confidence Level

2.0

rms

68%

3.0

rms

87%

4.0

rms

95.40%

5.0

rms

98.80%

6.0

rms

99.73%

6.6

rms

99.90%

Noise rms = 3.5mVrms

Noise peak to peak at a 99.9% confidence level:
3.5mVrms* 6.6 = 23.1mVpp

SelfTest

XMMA sensors provide a selftest 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 gcell as a self
test plate. This plate is fixed and is located under an ex-
tended portion of the center (moveable) plate. When the user
applies a logic high input to the selftest pin, a calibrated po-
tential is applied across the selftest 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 propor-
tional output voltage results. This procedure assures that
both the mechanical (gcell) and electronic sections of the
sensor are functioning.

Ratiometricity

The XMMA1000P and XMMA2000W are designed to be

"ratiometric''. That is, their transfer function will be propor-
tional to the applied supply voltage. This feature allows easy
interfacing to common microcontrollers that use ratiometric
A/D converters for system cost benefits.

In operation, a ratiometric sensor's gain or "sensitivity'' will

change 1:1 with applied supply voltage and the zero signal
output will be at midsupply. (2.5 V for a 5 V VDD and 2.625 V
for a 5.25 VDD).

Minimum G Range Calculation

To calculate the minimum g range values of an accelerom-

eter several factors have to be taken into consideration.
These considerations include, the supply voltage, the
device's sensitivity, offset voltage and output rail. A sample
calculation for the minimum g range is shown below.

To complete the calculation the rail and offset voltages

must be subtracted from the supply voltage, then divided by
the supply voltage multiplied by the device's worst case
(highest) sensitivity.

0.56V

0.3V

(8.64mV V g)

0.44V

0.3V

(0.00864)

50.93

34.72

Using the standard five volt power supply, the minimum g

range is calculated to be:

50.926

34.722

5.00

43.98

[

44g

XMMA1000P XMMA2000W

Motorola Sensor Device Data

BASIC CONNECTIONS

Circuit Schematic

Figure 3 shows the recommended connection diagram for

operating the accelerometer. Figure 3 (a) shows the 16 pin
DIP package version, the XMMA1000P, while (b) shows the
6 pin Wingback package version, the XMMA2000W. For the
XMMA1000P, pins 1, 2, 3, 6, 14, 15, and 16 have no internal
connections, and pins 9 through 13 are used for calibration
and trimming in the factory. These pins should all be con-
nected to VSS, except pin 11 which must be connected to
VDD. For the XMMA2000W, pins 1 and 4, and the wings
(supporting pins) should be connected to VSS.

XMMA1000P

VDD

TRIM 3

VSS

VOUT

OUTPUT
SIGNAL

1 k

0.01

LOGIC

INPUT

VDD

0.1

(a)

XMMA2000W

VDD

VSS

VOUT

OUTPUT
SIGNAL

1 k

0.01

LOGIC

INPUT

VDD

0.1

(b)

Figure 3. Accelerometers with Recommended

Connection Diagram

PCB Layout

A/D IN

VRH

VSS

VDD

VOUT

VSS

VDD

0.01

1 k

0.1

C 0.1

POWER SUPPLY

0.1

MICROCONTROLLER

ACCELEROMETER

NOTES:

Use a .1

F 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 above.

Use independent supply traces for the A/D reference
(microcontroller) and the accelerometer.

Use an RC filter of 1 k

and 0.01

F on the output of the

accelerometer to minimize induced errors.

PCB layout of power and ground should not couple power
supply noise.

Accelerometer and microcontroller should not be a high
current path.

For ratiometricity purposes the accelerometer VDD and mi-
crocontroller A/D reference pin should be on the same
trace.

A/D sampling rate and any external power supply switching
frequency should be selected such that they do not inter-
fere with the internal accelerometer sampling frequency.
This will prevent aliasing errors.

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 under its patent rights nor the rights of
others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other
applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury
or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola
and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees
arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that
Motorola was negligent regarding the design or manufacture of the part. Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal
Opportunity/Affirmative Action Employer.

XMMA1000P XMMA2000W

Motorola Sensor Device Data

PACKAGE DIMENSIONS

CASE 648C03

ISSUE C

DIP PACKAGE

A

B

NOTE 5

16 PL

0.13 (0.005)

T

SEATING
PLANE

0.13 (0.005)

16 PL

DIM

MIN

MAX

MIN

MAX

MILLIMETERS

INCHES

0.740

0.840

18.80

21.34

0.240

0.260

6.10

6.60

0.145

0.185

3.69

4.69

0.015

0.021

0.38

0.53

0.050 BSC

1.27 BSC

0.040

0.70

1.02

1.78

0.100 BSC

2.54 BSC

0.008

0.015

0.20

0.38

0.115

0.135

2.92

3.43

0.300 BSC

7.62 BSC

0.015

0.040

0.39

1.01

NOTES:

1. DIMENSIONING AND TOLERANCING PER ANSI

Y14.5M, 1982.

2. CONTROLLING DIMENSION: INCH.
3. DIMENSION L TO CENTER OF LEADS WHEN

FORMED PARALLEL.

4. DIMENSION B DOES NOT INCLUDE MOLD FLASH.
5. INTERNAL LEAD CONNECTION BETWEEN 4 AND

5, 12 AND 13.

CASE 45603

ISSUE D

WB PACKAGE

DIM

MIN

MAX

MIN

MAX

MILLIMETERS

INCHES

15.70

0.638

0.618

16.21

6.35

0.270

0.250

6.86

3.30

0.135

0.130

3.43

0.38

0.021

0.015

0.53

8.33

0.368

0.328

9.35

0.100 BSC

2.54 BSC

0.050 BSC

1.27 BSC

0.009

0.012

0.23

0.30

0.125

0.140

3.18

3.56

0.063

0.070

1.60

1.78

0.015

0.025

0.38

0.64

0.036

0.044

0.91

1.12

0.110

0.120

2.79

3.05

NOTES:

1. DIMENSIONING AND TOLERANCING PER ANSI

Y14.5M, 1982.

2. CONTROLLING DIMENSION: INCH.

A

0.13 (0.005)

6 PL

B

T

2.84

0.112

3.05

0.120

0.025

0.035

0.64

0.89

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XMMA1000P/D

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