MMA3202DR2 - Motorola / Freescale Semiconductor

Motorola Sensor Device Data MMA3202D

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 Wafer Level for Superior Reliability

•Robust Design, High Shocks Survivability

Typical Applications

•Vibration Monitoring and Recording

•Impact Monitoring

•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

G--CELL

SENSOR INTEGRATOR GAIN FILTER TEMP

COMP

SELF--TEST CONTROL LOGIC &

EPROM TRIM CIRCUITS CLOCK GEN.

OSCILLATOR

VDD

XOUT

VSS

Figure 1. Simplified Accelerometer Functional Block Diagram

STATUS

YOUT

AVDD

REV 0

Order this document

by MMA3202D/D

MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

MMA3202D

MMA3202D: X--Y AXIS SENSITIVITY

MICROMACHINED

ACCELEROMETER

±100/50g

20 LEAD SOIC

CASE 475A

N/C

XOUT

STATUS

VDD

GND

N/C

Pin Assignment

VSS

AVDD

N/C

YOUT

N/C

Motorola, Inc. 2003

2Motorola Sensor Device Data

MMA3202D

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 ±200 g

Unpowered Acceleration (all axes) Gupd 2000 g

Supply Voltage VDD --0.3to+7.0 V

Drop Test(1) Ddrop 1.2 m

Storage Temperature Range Tstg --40 to +105 °C

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

2000 volts can accumulate on the human body or associated

test equipment. A charge of this magnitude can alter the per-

formance or cause failure of the chip. When handling the ac-

celerometer, proper ESD precautions should be followed to

avoid exposing the device to discharges which may be detri-

mental to its performance.

Motorola Sensor Device Data MMA3202D

OPERATING CHARACTERISTICS

(Unless otherwise noted: --40°C≤TA≤+105°C, 4.75 ≤VDD ≤5.25, X and Y Channels, Acceleration = 0g, Loaded output(1))

Characteristic Symbol Min Typ Max Unit

Operating Range(2)

Supply Voltage(3)

Supply Current

Operating Temperature Range

Acceleration Range X--axis

”Acceleration Range Y--axis

VDD

IDD

gFS

4.75

−40

—

5.00

—

112.5

56.3

5.25

+85

—

°C

Output Signal

Zerog(V

DD =5.0V)

(4)

Zero g

Sensitivity X--axis (TA=25°C, VDD =5.0V)

(5)

Sensitivity Y--axis (Ta = 25°C, VDD =5.0V)

(5)

Sensitivity X--axis

Sensitivity Y--axis

Bandwidth Response

Nonlinearity

VOFF

VOFF,V

f--3dB

NLOUT

2.2

0.44 VDD

3.72

7.44

360

−1.0

2.5

0.50 VDD

400

—

2.8

0.56 VDD

4.28

8.56

440

+1.0

mV/g

mV/g/V

%FSO

Noise

RMS (.01--1 kHz)

Power Spectral Density

Clock Noise (without RC load on output)(6)

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

9.6

VSS

0.7 x VDD

−30

—

−110

2.0

14.4

0.3 x VDD

VDD

−300

—

µA

Status(12)(13)

Output Low (Iload = 100 µA)

Output High (Iload = 100 µA) VOL

VOH

—

VDD −.8 —

—0.4

—V

Minimum Supply Voltage (LVD Trip) VLVD 2.7 3.25 4.0 V

Clock Monitor Fail Detection Frequency fmin 50 —260 kHz

Output Stage Performance

Electrical Saturation Recovery Time(9)

Full Scale Output Range (IOUT = 200 µA)

Capacitive Load Drive(10)

Output Impedance

tDELAY

VFSO

—

0.3

—

0.2

—

300

—

VDD −0.3

100

—

Ω

Mechanical Characteristics

Transverse Sensitivity(11)

Package Resonance VZX,YX

fPKG

—

——

10 5.0

—%FSO

kHz

NOTES:

1. For a loaded output the measurements are observed after an RC filter consisting of a 1 kΩresistor 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. Thedevicecanmeasureboth+and−acceleration.Withnoinputaccelerationtheoutputisatmidsupply.Forpositiveaccelerationtheoutput

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, orthe 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.

4Motorola Sensor Device Data

MMA3202D

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 inte-

grated 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 semicon-

ductor processes (masking and etching). It can be modeled

as a set of beams attached to a movable central mass that

move between fixed beams. The movable beams can be de-

flected from their rest position by subjecting the system to an

acceleration. As the beams attached to the central mass

move the 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. The

g--cell beams form two back--to--back capacitors (Figure 2).

As the central mass moves with acceleration, the distance

between the beams change and each capacitor’s value will

change, (C = NAe/D). Where A is the area of the facing side

of the beam, e is the dielectric constant, and D is the distance

between the beams and N is the number of beams.

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 ratio-

metric and proportional to acceleration.

Acceleration

Figure 2. Simplified Transducer Physical Model

versus Transducer Physical 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 fil-

ter is realized using switched capacitor techniques, there is

no requirement for external passive components (resistors

and capacitors) to set the cut--off frequency.

Self--Test

The sensor provides a self--test feature that allows the ver-

ification of the mechanical and electrical integrity of the ac-

celerometer 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 elec-

trostatic force (Fe = 1/2AV2/d2) causes the center plate to

deflect. The resultant deflection is measured by the accel-

erometer’s control ASIC and a proportional output voltage re-

sults. 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

Pinout Description

N/C

XOUT

STATUS

VDD

GND

N/C

VSS

AVDD

N/C

YOUT

N/C

Motorola Sensor Device Data MMA3202D

Pin No. Pin

Name Description

1thru3 —Redundant Vss. Leave unconnected.

4 — No internal connection. Leave

unconnected.

5ST Logic input pin used to initiate

self--test.

6 XOUT Output voltage of the accelerometer.

X Direction.

7STATUS Logic output pin to indicate fault.

8 VSS The power supply ground.

9 VDD Power supply input.

10 AVDD Power supply input (Analog).

11 YOUT Output voltage of the accelerometer.

Y Direction.

12 thru 16 —Used for factory trim. Leave

unconnected.

17 thru 19 —No internal connection. Leave

unconnected.

20 —Ground.

XOUT

YOUT

MMA3202D

VDD

VSS

XOUTPUT

SIGNAL

1kΩ

0.01 µF

LOGIC

INPUT

VDD

0.1 µF

Figure 3. SOIC Accelerometer with Recommended

Connection Diagram

STATUS

YOUTPUT

SIGNAL

0.01 µF

1kΩ

AVDD

PCB Layout

A/D IN

VRH

VSS

VDD

YOUT

VSS

VDD

0.01 µF

1kΩ

0.1 µF

C0.1 µF

POWER SUPPLY

0.1 µF

MICROCONTROLLER

ACCELEROMETER

Figure 4. Recommend PCB Layout for Interfacing

Accelerometer to Microcontroller

P1STATUS

A/D IN

XOUT R

0.01 µF

1kΩ

NOTES:

•Usea0.1µF capacitor on VDD to decouple the power

source.

•Physical coupling distance of the accelerometer to the mi-

crocontroller should be minimal.

•Placeagroundplanebeneaththeaccelerometertoreduce

noise, the ground plane should be attached to all of the

open ended terminals shown in Figure 4.

•Use an RC filter of 1 kΩand 0.01 µF on the outputs of the

accelerometertominimizeclocknoise(fromtheswitched

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/Dsamplingrateandanyexternalpowersupplyswitching

frequency should be selected such that they do not inter-

fere with the internal accelerometer sampling frequency.

This will prevent aliasing errors.

6Motorola Sensor Device Data

MMA3202D

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

Positive Acceleration Sensing Direction

20--Pin SOIC Package

N/C pins are recommended to be left FLOATING

-- X + X

Direction of Earth’s gravity field.*

Front View

Top View

Side View

14 15 16 17 18 19 20

87654321

10 9

-- Y

ORDERING INFORMATION

Device Temperature Range Case No. Package

MMA3202D −40 to +105°CCase 475A--01 SOIC--20

MMA3202DR2 −40 to +105°CCase 475A--01 SOIC--20, Tape & Reel

Motorola Sensor Device Data MMA3202D

PACKAGE DIMENSIONS

CASE 475A--01

ISSUE O

20--LEAD SOIC

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.

DIM MIN MAX MIN MAX

INCHESMILLIMETERS

A12.67 12.96 0.499 0.510

B7.40 7.60 0.292 0.299

C3.30 3.55 0.130 0.140

D0.35 0.49 0.014 0.019

F0.76 1.14 0.030 0.045

G1.27 BSC 0.050 BSC

J0.25 0.32 0.010 0.012

K0.10 0.25 0.004 0.009

M0707

P10.16 10.67 0.400 0.420

R0.25 0.75 0.010 0.029

____

110

20 11

-- T --

-- B --

-- A --

P10 PL

D16 PL

0.13 (0.005) B M

RX45_

SEATING

PLANE

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 inter-

face between the board and the package. With the correct

footprint, 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 short-

ing between solder pads.

Figure 5. Footprint SOIC--20 (Case 475A--01)

0.380 in.

9.65 mm

0.050 in.

1.27 mm

0.024 in.

0.610 mm

0.080 in.

2.03 mm

8Motorola Sensor Device Data

MMA3202D

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EMotorola Inc. 2003

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MMA3202D/D

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