MMA6331LT - Freescale Semiconductor

Document Number: MMA6331L

Rev 1, 08/2011

Freescale Semiconductor

Data Sheet: Technical Data

±4g, ±9g Two Axis Low-g

Micromachined Accelerometer

The MMA6331L is a low power, low profile capacitive micromachined

accelerometer featuring signal conditioning, a 1-pole low pass filter,

temperature compensation, and g-Select which allows for the selection

between two sensitivities. Zero-g offset and sensitivity are factory set and

require no external devices. The MMA6331L includes a Sleep Mode th at

makes it ideal for handheld battery po wered electronics.

Features

• 3mm x 5mm x 1.0mm LGA-14 Package

• Low Current Consumption: 400 μA

• Sleep Mod e : 3 μA

• Low Voltage Operation: 2.2 V – 3.6 V

• Selectable Sensitivity (±4g, ±9g)

• Fast Turn On Time (0.5 ms Enable Response Time)

• Signal Conditioning with Low Pass Filter

• Robust Design, High Shocks Survivability

• RoHS Compliant

• Environmentally Preferred Product

• Low Cost

Typical Applications

• 3D Gaming: Tilt and Motion Sensing, Event Recorder

• HDD MP3 Player

• Laptop PC: Anti-Theft

• Cell Phone: Image Stability, Text Scroll, Motion Dialing, eCompass

• Pedometer: Motion Sensing

• PDA: Text Scroll

• Robotics: Motion Sensing

ORDERING INFORMATION

Part Number Temperature

Range Package

Drawing Package Shipping

MMA6331LT -40 to +85°C 1977-01 LGA-14 Tray

MMA6331LR1 -40 to +85°C 1977-01 LGA-14 7” Tape & Reel

MMA6331LR2 -40 to +85°C 1977-01 LGA-14 13” Tape & Reel

MMA6331L

MMA6331L: XY AXIS

ACCELEROMETER

±4g, ±9g

14 LEAD

LGA

CASE 1977-01

Bottom View

Figure 1. Pin Connectio ns

Top View

123456

8 9 10 11 12 13

N/C

OUT

Sleep

N/C

g-Select

N/C

GND

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MMA6331L

Figure 2. Simplified Accelerometer Functional Block Diagram

ELECTRO STATIC DISCHARGE (ESD)

WARNING: This device is sensitive to electrostatic

discharge.

Although the Freescale accelerometer contains internal

2000 V 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 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.

Table 1. Maximum Ratings

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

Rating Symbol Value Unit

Maximum Acceleration (all axis) gmax ±5000 g

Supply Voltage VDD –0.3 to +3.6 V

Drop Test(1)

1. Dropped onto concrete surface from any axis.

Ddrop 1.8 m

Storage Temperature Range Tstg –40 to +125 °C

C to V

CONVERTER

XOUT

YOUT

OSCILLATOR CLOCK

GEN

Sleep

X-TEMP

COMP

G-CELL

SENSOR GAIN

FILTER

CONTROL LOGIC

NVM TRIM

CIRCUITS

Y-TEMP

COMP

VDD

VSS

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Table 2. Operating Characteristics

Unless otherwise noted: -40°C < TA < 85°C, 2.2 V < VDD < 3.6 V, Acceleration = 0g, Loaded output(1)

Characteristic Symbol Min Typ Max Unit

Operating Range(2)

Supply Voltage(3)

Supply Current(4)

Supply Current at Sleep Mode(4)

Operating Temperature Range

Acceleration Range, X-Axis, Y-Axis

g-Select: 0

g-Select: 1

VDD

IDD

gFS

2.2

—

-40

—

2.8

400

—

±4

±9

3.6

600

+85

—

μA

°C

Output Signal

Zero g (TA = 25°C, VDD = 2.8 V)(5), (6)

Zero g(7)

Sensitivity (TA = 25°C, VDD = 2.8 V)

Sensitivity(4)

Bandwidth Response

Output Impedance

VOFF

VOFF, TA

S4g

S9g

S,TA

f-3dBXY

1.316

-2.0

289.5

75.2

-0.0075

—

1.4

±0.5

308

83.6

±0.002

400

1.484

+2.0

326.5

91.9

+0.0075

—

mg/°C

mV/g

%/°C

kΩ

Noise

Power Spectral Density RMS (0.1 Hz – 1 kHz)(4) nPSD — 350 — μg/

Control Timing

Power-Up Response Time(8)

Enable Response Time(9)

Sensing Element Resonant Frequency

Internal Sampling Frequency

tRESPONSE

tENABLE

fGCELLXY

fCLK

—

1.0

0.5

6.0

2.0

—

kHz

Output Stage Performance

Full-Scale Output Range (IOUT = 3 µA) VFSO VSS+0.1 — VDD–0.1 V

Nonlinearity, XOUT, YOUT NLOUT -1.0 — +1.0 %FSO

Cross-Axis Sensitivity(10) V

XY -5.0 — +5.0 %

1. For a loaded output, the measurements are observed after an RC filter consisting of an internal 32 kΩ resistor and an external 3.3 nF capacitor

(recommended as a minimum to filter clock noise) on the analog output for each axis and a 0.1 μF capacitor on VDD - GND. The output sensor

bandwidth is determined by the Capacitor added on the output. f = 1/2π * (32 x 103) * C. C = 3.3 nF corresponds to BW = 1507HZ, which is

the minimum to filter out internal clock noise.

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

3. Within the supply range of 2.2 and 3.6 V, 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. This value is measured with g-Select in 4g mode.

5. 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. For negative acceleration, the output will decrease below VDD/2.

6. For optimal 0g offset performance, adhere to AN3484 and AN3447.

7.Product Performance will not exceed this minimum level, however, measurement over time will not be equal to time zero measurements for

this specific parameter.

8. The response time between 10% of full scale VDD input voltage and 90% of the final operating output voltage.

9. The response time between 10% of full scale Sleep Mode input voltage and 90% of the final operating output voltage.

10. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity

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MMA6331L

PRINCIPLE OF OPERATION

The Freescal e accelerometer is a s urface-micromachined

integrated-circuit accelerometer.

The device consists of a surface micromachined

capacitive sensing cell (g-cell) and a signal conditioning ASIC

contained in a single 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 semiconducto r

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 deflected

from their rest position by subjecting the system to an

acceleration (Figure 3).

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 3). As the center beam moves with acceleration, the

distance between the beams changes and each capacitor's

value will change, (C = Aε/D). Where A is the area of the

beam, ε is the dielectric constant, and D is the distance

between the beams.

The 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.

Figure 3. Simplified Transducer Physical Model

SPECIAL FEATURES

g-Select

The g-Select feature allows for the selection between two

sensitivities. Depending on the logic input placed on pin 10,

the device internal gain will be changed allowing it to function

with a 4g or 9g sensitivity (Table 3). This feature is ideal when

a product has applications requiring two different sensitivities

for optimum performance. The sensitivity can be changed at

anytime during the operation of the product. The g-Select pin

can be left unconnected for applications requiring only a 4g

sensitivity as the device has an internal pull-down to keep it

at that sensitivity (308 mV/g).

Sleep Mode

The 2 axis acceleromete r pro v ides a Sleep Mode that is

ideal for battery operated products. When Sleep Mode is

active, the device outputs are turned off, providing significant

reduction of operating current. A low input signal on pin 7

(Sleep Mode) will place the device in this mode and reduce

the current to 3 μA typ. For lower power consumption, it is

recommended to set g-Select to 4g mode. By placing a high

input signal on pin 7, the device will resume to normal mode

of operation.

Filtering

The 2 axis accelerometer contains an onboard single-pole

switched capacitor filter. 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.

Ratiometricity

Ratiometricity simply means the output offset volt age and

sensitivity will scale linearly with applied supply voltage. That

is, as supply voltage is increased, 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.

Acceleration

Table 3. g-Select Pin Descripti on

g-Select g-Range Sensitivity

04g 308 mV/g

19g 83.6 mV/g

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MMA6331L

BASIC CONNECTIONS

Pin Descriptions

Figure 4. Pinout Description

Figure 5. Acce lerometer with Recommended

Connection Diagram

PCB Layout

Figure 6. Recommende d PCB La y out for Interfacing

Accelerometer to Microcontroller

NOTES:

1. Use 0.1 µF capacitor on VDD to decouple the power

source.

2. Physical coupling distance of the accelerometer to

the microcontroller should be minimal.

3. 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 6.

4. Use a 3.3 nF capacitor on the outputs of the

accelerometer to minimize clock noise (from the

switched capacitor filter circuit).

5. PCB layout of power and ground should not couple

power supply noise.

6. Accelerometer and microcontroller should not be a

high current path.

7. A/D sampling rate and any external power supply

switching frequency should be selected such that

they do not inte rfere with the internal accelerometer

sampling frequency (11 kHz for the sampling

frequency). This will prevent aliasing errors.

8. 10 MΩ or higher is recommended on XOUT and YOUT

to prevent loss due to the voltage divider relationship

between the internal 32 kΩ resistor and the

measurement input impedance.

Table 4. Pin Descriptions

Pin No.

Pin Name Description

1 N/C No internal connection

Leave unconnected

OUT X direction output voltage

OUT Y direction output voltage

4 N/C No internal connection

Leave unconnected

5 VSS Power Supply Ground

DD Power Supply Input

7Sleep

Logic input pin to enable product or Sleep Mode

8 N/C No internal connection

Leave unconnected

9 N/C No internal connection

Leave unconnected

10 g-Select Logic input pin to select g level

11 N/C Unused for factory trim

Leave unconnected

12 N/C Unused for factory trim

Leave unconnected

13 GND Connect to Ground

14 N/C Unused for factory trim

Leave unconnected

123456

8 9 10 11 12 13

N/C

XOUT

YOUT

VSS

VDD

Sleep

N/C

g-Select

N/C

GND

Top View

3.3 nF

Logic

Input

0.1 μF

VDD

VSS

GND

Sleep

XOUT

YOUT

MMA6331L

Logic

Input g-Select

POWER SUPPLY

VDD

VSS

Sleep

g-Select

OUT

Accelerometer

VDD

VSS

VRH

A/DIN

CCC

Microcontroller

GND

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MMA6331L

Top View

-Y

+X-X

: Arrow indicates direction of package movement.

14-Pin LGA Package

123456

8 9 10 11 12 13

Side View

XOUT @0g=1.4V

YOUT @ +1g = 1.708 V

XOUT @ +1g = 1.708 V

YOUT @0g=1.4V

XOUT @ -1g = 1.092 V

YOUT @0g=1.4V

XOUT @0g=1.4V

YOUT @ -1g = 1.092 V

Direction of Earth's gravity field.*

Top View

XOUT @0g=1.4V

YOUT @0g=1.4V

XOUT @0g=1.4V

YOUT @0g=1.4V

Top

Bottom

123456

8 9 10 11 12 13

123456

8 9 10 11 12 13

13 12 11 10 9 8

12 34 56

14 7

123456

8 9 10 11 12 13

DYNAMIC ACCELERATION

STATIC ACCELERATION

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

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MMA6331L

Figure 7. MMA6331L Temperature Coefficient of Offset (T CO) and

Temperature Coefficient of Sensitivity (TC S) Distributio n Charts

LSL USLTarget

-2 -1 0 1 2

X-TCO mg/degC

LSL USLTarget

-2 -1 0 1 2

Y-TCO mg/degC

LSL USLTarget

-0.01 -0.005 0.005 .01

X-TCS %/degC

LSL USLTarget

-0.01 -0.005 0.005 .01

Y-TCS %/degC

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MMA6331L

MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS

PCB Mounting Recommendations

MEMS based sensors are sensitive to Printed Circuit

Board (PCB) reflow processes. For optimal zero-g offset after

PCB mounting, care must be taken to PCB layout and reflow

conditions. Reference application note AN3484 for best

practices to minimize the zero-g offset shift after PCB

mounting.

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, 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 shorti ng between solder pads.

Figure 8. LGA 14-Lead, 5 x 3 mm Die Sensor

6x2

12x1

14x0.9

14x0.6

10x0.8

113

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Freescale Semiconductor 9

MMA6331L

PACKAGE DIMENSIONS

CASE 1977-01

ISSUE A

14-LEAD LGA

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MMA6331L

PACKAGE DIMENSIONS

CASE 1977-01

ISSUE A

14-LEAD LGA

MMA6331L

Rev. 1

08/2011

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