LIS244ALTR - STMicroelectronics - Datasheet.Directory

June 2007 Rev 1 1/15

LIS244AL

MEMS motion sensor:

2-axis - ±2g ultracompact linear accelerometer

Features

■Single voltage supply operation

■± 2g full-scale

■Output voltage, offset and sensitivity are

ratiometric to the supply voltage

■Factory trimmed device sensitivity and offset

■Embedded self test

■ECOPACK lead-free compliant

■High shock survivability (10000g)

Description

The LIS244AL is an ultra compact consumer low-

power two-axis linear accelerometer that includes

a sensing element and an IC interface able to take

the information from the sensing element and to

provide an analog signal to the external world.

The sensing element, capable of detecting the

acceleration, is manufactured using a dedicated

process developed by ST to produce inertial

sensors and actuators in silicon. The IC interface

is manufactured using a CMOS process that

allows high level of integration to design a

dedicated circuit which is trimmed to better match

the sensing element characteristics.

The LIS244AL is capable of measuring

accelerations over a maximum bandwidth of

2.0kHz. The device bandwidth may be reduced by

using external capacitances. A self-test capability

allows the user to check the functioning of the

system.

The LIS244AL is available in Land Grid Array

package (LGA) and it is guarantee to operate over

an extended temperature range of -40°C to

+85°C.

The LIS244AL belongs to a family of products

suitable for a variety of applications:

– Mobile terminals

– Gaming and Virtual Reality input devices

– Antitheft systems and Inertial Navigation

– Appliance and Robotics.

Note: Tape & Reel parts are compliant to International Standard EIA-481.

LGA 16

(4x4x1.5mm)

Table 1. Device summary

Order codes Temp range, °CPackage Packing

LIS244AL -40°C to +85°C LGA-16 Tray

LIS244ALTR -40°C to +85°C LGA-16 Tape & Reel

www.st.com

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Contents LIS244AL

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Contents

1 Block diagram & pins description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Mechanical and electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.3 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.1 Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2 IC Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4 Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.1 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4.2 Output Response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

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LIS244AL Block diagram & pins description

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1 Block diagram & pins description

1.1 Block diagram

Figure 1. Block diagram

1.2 Pin Description

Figure 2. Pin Connection

S/H

Routx

Routy

REFERENCE TRIMMING CIRCUIT CLOCK

CHARGE

AMPLIFIER

MUX DEMUX

Voutx

Vouty

Y+

Y-

X+

X-

SELF TEST

(TOP VIEW)

DIRECTION OF THE

DETECTABLE

ACCELERATIONS (BOTTOM VIEW)

GND

VoutX

Vouty

GND

Vdd

res

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Block diagram & pins description LIS244AL

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Table 2. Pin description

Pin # Pin name Function

1 NC Not to be connected

2 ST Self test (logic 0: normal mode; logic 1: self-test mode)

3 GND 0V supply

4 NC Not to be connected

5 GND 0V supply

6 GND 0V supply

7 GND 0V supply

8 NC Not to be connected

9 NC Not to be connected

10 Vouty Output voltage Y channel

11 NC Not to be connected

12 Voutx Output voltage X channel

13 NC Not to be connected

14 Vdd Power supply

15 Res Connect to Vdd

16 NC Not to be connected

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LIS244AL Mechanical and electrical specifications

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2 Mechanical and electrical specifications

2.1 Mechanical characteristics

(Temperature range -40°C to +85°C). All the parameters are specified @ Vdd =3.0V,

T = 25°C unless otherwise noted

Table 3. Mechanical characteristics(1)

Symbol Parameter Test condition Min. Typ.(2) Max. Unit

Ar Acceleration range(3) ±2g

So Sensitivity(5) 0.140*Vdd -

10% 0.140*Vdd 0.140*Vdd+

10% V/g

SoDr Sensitivity change vs

temperature Delta from +25°C 0.01 %/°C

Voff Zero-g level(4) T = 25°C Vdd/2-15% Vdd/2 Vdd/2+15% V

OffDr Zero-g level change vs

temperature Delta from +25°C 1 mg/°C

NL Non linearity(5) Best fit straight line ±0.5 % FS

CrossAx Cross-axis(6) ±2%

An Acceleration noise

density Vdd=3.0V 220 µg/

Vt Self test output voltage

change(7),

T = 25°C

Vdd=3.0V

X axis

105 mV

T = 25°C

Vdd=3.0V

Y axis

105 mV

Fres Sensing element

resonant frequency(8) X,Yaxis 4.0 kHz

To p Operating temperature

range -40 +85 °C

Wh Product weight 0.040 gram

1. The product is factory calibrated at 3.0V. The operational power supply range is from 2.4V to 3.6V. Voff, So and Vt

parameters will vary with supply voltage

2. Typical specifications are not guaranteed

3. Guaranteed by wafer level test and measurement of initial offset and sensitivity

4. Zero-g level and sensitivity are essentially ratiometric to supply voltage at the calibration level ±8%

5. Guaranteed by design

6. Contribution to the measuring output of an inclination/acceleration along any perpendicular axis

7. “Self test output voltage change” is defined as Vout(Vst=Logic1)-Vout(Vst=Logic0)

8. Minimum resonance frequency Fres=4.0kHz. Sensor bandwidth=1/(2*π*32kΩ*Cload)

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Mechanical and electrical specifications LIS244AL

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2.2 Electrical characteristics

(Temperature range -40°C to +85°C) All the parameters are specified @ Vdd =3.0V, T=25°C

unless otherwise noted

Table 4. Electrical characteristics(1)

1. The product is factory calibrated at 3.0V

Symbol Parameter Test condition Min. Typ.(2)

2. Typical specifications are not guaranteed

Note: Minimum resonance frequency Fres=4.0kHz. Device

bandwidth=1/(2*

*32k

Ω

*Cload)

Max. Unit

Vdd Supply voltage 2.4 3.0 3.6 V

Idd Supply current 0.65 mA

Vst Self test input Logic 0 level 0 0.8 V

Logic 1 level 2.0 Vdd V

Rout Output impedance

of Voutx, Vouty 32 kΩ

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LIS244AL Mechanical and electrical specifications

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2.3 Absolute maximum ratings

Stresses above those listed as “absolute maximum ratings” may cause permanent damage

to the device. This is a stress rating only and functional operation of the device under these

conditions is not implied. Exposure to maximum rating conditions for extended periods may

affect device reliability.

2.4 Terminology

Sensitivity describes the gain of the sensor and can be determined by applying 1g

acceleration to it. As the sensor can measure DC accelerations this can be done easily by

pointing the axis of interest towards the center of the earth, note the output value, rotate the

sensor by 180 degrees (point to the sky) and note the output value again thus applying ±1g

acceleration to the sensor. Subtracting the larger output value from the smaller one and

dividing the result by 2 will give the actual sensitivity of the sensor. This value changes very

little over temperature (see sensitivity change vs. temperature) and also very little over time.

The sensitivity tolerance describes the range of sensitivities of a large population of sensors.

Zero-g level describes the actual output signal if there is no acceleration present. A sensor

in a steady state on a horizontal surface will measure 0g in X axis and 0g in Y axis. The

output is ideally for a 3.0V powered sensor Vdd/2 = 1500mV. A deviation from ideal 0-g level

(1500mV in this case) is called Zero-g offset. Offset of precise MEMS sensors is to some

extend a result of stress to the sensor and therefore the offset can slightly change after

mounting the sensor onto a printed circuit board or exposing it to extensive mechanical

stress. Offset changes little over temperature - see “Zero-g level change vs. temperature” -

the Zero-g level of an individual sensor is very stable over lifetime. The Zero-g level

tolerance describes the range of Zero-g levels of a population of sensors.

Table 5. Absolute maximum ratings

Symbol Ratings Maximum value Unit

Vdd Supply voltage -0.3 to 6 V

Vin Input voltage on any control pin (ST) -0.3 to Vdd +0.3 V

APOW Acceleration (any axis, powered, Vdd=3.0V) 3000g for 0.5 ms

10000g for 0.1 ms

AUNP Acceleration (any axis, not powered) 3000g for 0.5 ms

10000g for 0.1 ms

TSTG Storage temperature range -40 to +125 °C

This is a Mechanical Shock sensitive device, improper handling can cause permanent

damages to the part

This is an ESD sensitive device, improper handling can cause permanent damages to the

part

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Mechanical and electrical specifications LIS244AL

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Self Test allows to test the mechanical and electric part of the sensor, allowing the seismic

mass to be moved by means of an electrostatic test-force. The Self Test function is off when

the ST pin is connected to GND. When the ST pin is tied at Vdd an actuation force is applied

to the sensor, simulating a definite input acceleration. In this case the sensor outputs will

exhibit a voltage change in their DC levels which is depending on the supply voltage through

the device sensitivity. When ST is activated, the device output level is given by the algebraic

sum of the signals produced by the acceleration acting on the sensor and by the

electrostatic test-force. If the output signals change within the amplitude specified inside

Ta bl e 3 , than the sensor is working properly and the parameters of the interface chip are

within the defined specification.

Output impedance describes the resistor inside the output stage of each channel. This

resistor is part of a filter consisting of an external capacitor of at least 2.5nF and the internal

resistor. Due to the resistor level, only small inexpensive external capacitors are needed to

generate low corner frequencies. When interfacing with an ADC it is important to use high

input impedance input circuitries to avoid measurement errors. Note that the minimum load

capacitance forms a corner frequency close to the resonance frequency of the sensor. In

general the smallest possible bandwidth for a particular application should be chosen to get

the best results.

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LIS244AL Functionality

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3 Functionality

The LIS244AL is an ultra compact low-power, analog output two-axis linear accelerometer

packaged in a LGA package. The complete device includes a sensing element and an IC

interface able to take the information from the sensing element and to provide an analog

signal to the external world.

3.1 Sensing element

A proprietary process is used to create a surface micro-machined accelerometer. The

technology allows to carry out suspended silicon structures which are attached to the

substrate in a few points called anchors and are free to move in the direction of the sensed

acceleration. To be compatible with the traditional packaging techniques a cap is placed on

top of the sensing element to avoid blocking the moving parts during the moulding phase of

the plastic encapsulation.

When an acceleration is applied to the sensor the proof mass displaces from its nominal

position, causing an imbalance in the capacitive half-bridge. This imbalance is measured

using charge integration in response to a voltage pulse applied to the sense capacitor.

At steady state the nominal value of the capacitors are few pF and when an acceleration is

applied the maximum variation of the capacitive load is in pF range.

3.2 IC Interface

The complete signal processing uses a fully differential structure, while the final stage

converts the differential signal into a single-ended one to be compatible with the external

world.

The first stage is a low-noise capacitive amplifier that implements a Correlated Double

Sampling (CDS) at its output to cancel the offset and the 1/f noise. The produced signal is

then sent to two different S&Hs, one for each channel, and made available to the outside.

All the analog parameters (output offset voltage and sensitivity) are ratiometric to the

voltage supply. Increasing or decreasing the voltage supply, the sensitivity and the offset will

increase or decrease linearly. The feature provides the cancellation of the error related to

the voltage supply along an analog to digital conversion chain.

3.3 Factory calibration

The IC interface is factory calibrated for sensitivity (So) and Zero-g level (Voff).

The trimming values are stored inside the device by a non volatile structure. Any time the

device is turned on, the trimming parameters are downloaded into the registers to be

employed during the normal operation. This allows the user to employ the device without

further calibration.

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Application hints LIS244AL

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4 Application hints

Figure 3. LIS244AL Electrical connection

Power supply decoupling capacitors (100nF ceramic or polyester + 10µF Aluminum) should

be placed as near as possible to the device (common design practice).

The LIS244AL allows to band limit Voutx, Vouty through the use of external capacitors. The

recommended frequency range spans from DC up to 2.0kHz. In particular, capacitors are

added at output Voutx, Vouty pins to implement low-pass filtering for antialiasing and noise

reduction. The equation for the cut-off frequency (ft) of the external filters is in this case:

Equation 1

Taking into account that the internal filtering resistor (Rout) has a nominal value equal to

32kΩ, the equation for the external filter cut-off frequency may be simplified as follows:

Equation 2

Digital signals

LIS244AL

(top view)

(TOP VIEW)

DIRECTION OF THE

DETECTABLE

ACCELERATIONS

GND

Vdd

GND

100nF 10

Vout y

Optional

Cload y

Vout x

Cload x

Optional

678

15 14 13

Pin 1 indicator

2πRout Cload xy,()⋅⋅

----------------------------------------------------------------=

5µF

Cloadxy,

--------------------------Hz[]=

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LIS244AL Application hints

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The tolerance of the internal resistor can vary typically of ±20% within its nominal value of

32kΩ; thus the cut-off frequency will vary accordingly. A minimum capacitance of 2.5nF for

Cload(x, y) is required.

4.1 Soldering information

The LGA package is compliant with the ECOPACK, RoHs and “Green” standard.

Pin1 indicator is electrically connected to pin 1. Leave pin 1 indicator unconnected during

soldering.

4.2 Output Response vs. orientation

Figure 4. Output response vs. orientation

Figure 4 refers to LIS244AL powered at 3.0V.

Table 6. Filter Capacitor Selection, Cload (x,y),

Cut-off frequency Capacitor value

1 Hz 5 µF

10 Hz 0.5µF

20 Hz 250nF

50 Hz 100nF

100 Hz 50nF

200 Hz 25nF

500 Hz 10nF

Earth’s Surface

X=1.50V (0g)

Y=1.50V (0g)

TOP VIEW

X=1.50V (0g)

Y=1.83V (+1g)

X=1.50V (0g)

Y=1.17V (-1g)

X=1.17V (-1g)

Y=1.50V (0g)

X=1.83V (+1g)

Y=1.50V (0g)

Top

Bottom

X=1.50V (0g)

Y=1.50V (0g)

Top

Bottom

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Package information LIS244AL

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5 Package information

In order to meet environmental requirements, ST offers these devices in ECOPACK®

packages. These packages have a Lead-free second level interconnect. The category of

second Level Interconnect is marked on the package and on the inner box label, in

compliance with JEDEC Standard JESD97. The maximum ratings related to soldering

conditions are also marked on the inner box label. ECOPACK is an ST trademark.

ECOPACK specifications are available at: www.st.com.

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LIS244AL Package information

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Figure 5. LGA 16: mechanical data & package dimensions

Dimensions

Ref. mm inch

Min. Typ. Max. Min. Typ. Max.

A1 1 1.60 0.039 0.063

A2 1.33 0.052

A30.160 0.20 0.24 0.006 0.0080.009

D1 3.850 4.0 4.150 0.152 0.157 0.163

E1 3.850 4.0 4.150 0.152 0.157 0.163

L 0.65 0.026

L1 1.95 0.077

N0.98 0.039

N1 1.90 0.075

T1 0.40 0.016

T2 0.30 0.012

P1 1.750 0.069

P2 1.525 0.060

R0.30 0.012

S0.10 0.004

k0.05 0.0019

LGA 16 (4x4x1.5mm)

Outline and

7974136

mechanical data

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Revision history LIS244AL

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6 Revision history

Table 7. Document revision history

Date Revision Changes

29-Jun-2007 1 Initial release

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LIS244AL

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