MMA1220D - Freescale Semiconductor

1Motorola Sensor Device Data

Low G

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–of f 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 Shock 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

ORDERING INFORMATION

Device Temperature Range Case No. Package

MMA1220D –40 to +85°CCase 475–01 SOIC–16

SIMPLIFIED ACCELEROMETER FUNCTIONAL BLOCK DIAGRAM

G–CELL

SENSOR INTEGRATOR GAIN FILTER TEMP

COMP

SELF–TEST CONTROL LOGIC &

EPROM TRIM CIRCUITS CLOCK GEN.

OSCILLATOR

VDD

VOUT

VSS

Figure 1. Simplified Accelerometer Functional Block Diagram

STATUS

REV 0

Order this document

by MMA1220D/D

MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

MMA1220D

MMA1220D: Z AXIS SENSITIVITY

MICROMACHINED

ACCELEROMETER

±8g

16 LEAD SOIC

CASE 475–01

N/C

VOUT

STATUS

VSS

VDD

N/C

Pin Assignment

 Motorola, Inc. 2001

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MMA1220D

2 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 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

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

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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MMA1220D

3Motorola Sensor Device Data

OPERATING CHARACTERISTICS

(Unless otherwise noted: –40°C

+85°C, 4.75

VDD

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

Characteristic Symbol Min Typ Max Unit

Operating Range(2)

Supply Voltage(3)

Supply Current

Operating Temperature Range

Acceleration Range

VDD

IDD

gFS

4.75

3.0

—

5.00

5.0

—

8.0

5.25

6.0

+85

—

°C

Output Signal

Zero g (VDD = 5.0 V)(4)

Zero g

Sensitivity (TA = 25°C, VDD = 5.0 V)(5)

Sensitivity

Bandwidth Response

Nonlinearity

VOFF

VOFF,V

f–3dB

NLOUT

2.25

0.45 VDD

237.5

46.5

150

1.0

2.5

0.50 VDD

250

—

2.75

0.55 VDD

262.5

53.5

350

+3.0

mV/g

mV/g/V

% FSO

Noise

RMS (10 Hz – 1 kHz)

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

nCLK —

——

2.0 6.0

—mVrms

mVpk

Self–Test

Output Response

Input Low

Input High

Input Loading(7)

Response T ime (8)

VST

VIL

VIH

IIN

tST

0.2 VDD

VSS

0.7 VDD

—

100

2.0

0.3 VDD

VDD

200

µA

Status(12)(13)

Output Low (Iload = 100 µA)

Output High (Iload = 100 µA) VOL

VOH —

VDD

0.8 —

—0.4

—V

Minimum Supply Voltage (L VD T rip) VLVD 2.7 3.25 4.0 V

Clock Monitor Fail Detection Frequency fmin 50 — 260 kHz

Output Stage Performance

Electrical Saturation Recovery T ime(9)

Full Scale Output Range (IOUT = 200 µA)

Capacitive Load Drive(10)

Output Impedance

tDELAY

VFSO

—

VSS+0.25

—

2.0

—

300

—

VDD

0.25

100

—

Ω

Mechanical Characteristics

T ransverse Sensitivity(11)

Package Resonance VXZ,YZ

fPKG —

——

10 5.0

—% FSO

kHz

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, 100 Hz. Sensitivity limits apply to 0 Hz acceleration.

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 V oltage 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.

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MMA1220D

4 Motorola Sensor Device Data

PRINCIPLE OF OPERATION

The Motorola accelerometer is a surface–micromachined

integrated–circuit accelerometer.

The device consists of a surface micromachined capaci-

tive 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 semicon-

ductor materials (polysilicon) using semiconductor pro-

cesses (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 sub-

jecting 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 dis-

tance 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 ratio-

metric and proportional to acceleration.

Acceleration

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 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

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 elec-

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

deflect. The resultant deflection is measured by the accel-

erometer’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.

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MMA1220D

5Motorola Sensor Device Data

BASIC CONNECTIONS

N/C

VOUT

STATUS

VSS

VDD

N/C

Pinout Description

Pin No. Pin Name Description

1 thru 3 VSS Redundant connections to the internal

VSS and may be left unconnected.

4 ST Logic input pin used to initiate self–

test.

5 VOUT Output voltage of the accelerometer.

6 STATUS Logic output pin used to indicate fault.

7 VSS The power supply ground.

8 VDD The power supply input.

9 thru 13 Trim pins Used for factory trim.

Leave unconnected.

14 thru 16 —No internal connection.

Leave unconnected.

MMA1220D

VDD

VSS

VOUT OUTPUT

SIGNAL

1 kΩ

0.01 µF

LOGIC

INPUT

VDD

0.1 µF

Figure 4. SOIC Accelerometer with Recommended

Connection Diagram

STATUS

PCB Layout

A/D IN

VRH

VSS

VDD

VOUT

VSS

VDD

0.01 µF

1 kΩ

0.1 µF

C0.1 µF

POWER SUPPLY

0.1 µF

MICROCONTROLLER

ACCELEROMETER

Figure 5. Recommended PCB Layout for Interfacing

Accelerometer to Microcontroller

P1STATUS

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 inter-

fere with the internal accelerometer sampling frequency.

This will prevent aliasing errors.

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MMA1220D

6 Motorola Sensor Device Data

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

ACCELERATION SENSING DIRECTIONS

N/C

VOUT

STATUS

VSS

VDD

N/C

16–Pin SOIC Package

N/C pins are recommended to be left FLOATING

–g

Direction of Earth’s gravity field.*

DYNAMIC ACCELERATION

STATIC ACCELERA TION

[ VOUT > 2.75 ]

[ VOUT < 2.75 ]

–1g

+1g

0g 0g

VOUT = 2.50V VOUT = 2.50V

VOUT = 2.75V

VOUT = 2.25V

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MMA1220D

7Motorola Sensor Device Data

PACKAGE DIMENSIONS

CASE 475–01

ISSUE A

16 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

A10.15 10.45 0.400 0.411

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

M0 7 0 7

P10.16 10.67 0.400 0.420

R0.25 0.75 0.010 0.029

____

16 9

–T–

–B–

–A–

P8 PL

D16 PL

0.13 (0.005) B M

RX 45

SEATING

PLANE

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MMA1220D

8 Motorola Sensor Device Data

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.

How to reach us:

USA/EUROPE/Locations Not Listed: Motorola Literature Distribution; JAPAN: Motorola Japan Ltd.; SPS, Technical Information Center, 3–20–1,

P.O. Box 5405, Denver, Colorado 80217. 1–303–675–2140 or 1–800–441–2447 Minami–Azabu. Minato–ku, Tokyo 106–8573 Japan. 81–3–3440–3569

T echnical Information Center: 1–800–521–6274 ASIA/P AC IFIC: Motorola Semiconductors H.K. Ltd.; Silicon Harbour Centre,

2, Dai King Street, Tai Po Industrial Estate, Tai Po, N.T., Hong Kong.

852–26668334

HOME PAGE: http://www.motorola.com/semiconductors/

MMA1220D/D

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