STMicroelectronics LIS302ALKTR Mems motion sensor 3-axis-â±2g analog output "piccolo" accelerometer Datasheet

LIS302ALK
MEMS motion sensor
3-axis - ±2g analog output "piccolo" accelerometer
Preliminary Data
Features
■
3.0V to 3.6V supply voltage
■
~2mW power consumption
■
±2g full-scale
■
3 axes acceleration channels
■
Ratiometric output voltage
■
Embedded self test
■
Power down mode
■
10000g high shock survivability
■
ECOPACK® RoHS and “Green” compliant
(see Section 5)
LGA-14 (3x5x0.9mm)
Description
The LIS302ALK is a miniaturized low-power
three-axis linear accelerometer. It includes a
sensing element and an IC interface 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 motion
sensors and actuators in silicon.
The IC interface is manufactured using a CMOS
process that allows to design a dedicated circuit
which is trimmed to better match the sensing
element characteristics. The device can be
operated from 2.16V to 3.6V.
The LIS302ALK has a full scale of ±2g and it 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 sensor in the final application
without thew need to move or tilt the sensor.
The LIS302ALK is available in plastic Thin Land
Grid Array package (TLGA) and it is guaranteed
to operate over an extended temperature range
from -40°C to +85°C.
The LIS302ALK belongs to a family of products
suitable for a variety of applications:
– Mobile terminals
– Gaming and Virtual Reality input devices
– Free-fall detection for data protection
– Antitheft systems and Inertial Navigation
– Appliance and Robotics.
Order codes
Part number
Temperature range, °C
Package
Packing
LIS302ALK
-40°C to +85°C
LGA-14
Tray
LIS302ALKTR
-40°C to +85°C
LGA-14
Tape & reel
Note:
October 2006
Tape & reel parts are compliant to International Standard EIA-481.
Rev 1
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to
change without notice.
1/14
www.st.com
14
Contents
LIS302ALK
Contents
1
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1
2
3
4
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
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
Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1
Sensing element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2
IC interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3
Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1
Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2
Output response vs. orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2/14
LIS302ALK
1
Block diagram
Block diagram
Figure 1.
Block diagram
X+
CHARGE
AMPLIFIER
Y+
Z+
a
MUX
Routx
Voutx
Routy
Vouty
Routz
Voutz
S/H
DEMUX
S/H
ZYX-
S/H
REFERENCE
SELF TEST
1.1
TRIMMING CIRCUIT
CLOCK
Pin description
Figure 2.
Pin connection
Z
1
Y
8
Voutx
(TOP VIEW)
DIRECTION OF THE
DETECTABLE
ACCELERATIONS
Vdd
res
res
GND
Voutz
Vouty
1
res
res
res
res
ST
PD
LIS302AL
X
res
13
6
(BOTTOM VIEW)
3/14
Block diagram
LIS302ALK
Table 1.
4/14
Pin description
Pin #
Pin Name
Function
1
Reserved
Connect to Vdd
2
Reserved
Connect to Vdd
3
Reserved
Connect to Gnd
4
Reserved
Connect to Gnd
5
ST
Self Test (Logic 0: normal mode; Logic 1: Self-test)
6
PD
Power Down (Logic 0: normal mode; Logic 1: Power-Down mode)
7
Voutx
Output Voltage X channel
8
Vouty
Output Voltage Y channel
9
Voutz
Output Voltage Z channel
10
GND
0V supply
11
Reserved
Leave unconnected
12
Reserved
Connect to Gnd
13
Vdd
14
Reserved
Power supply
Connect to Vdd
LIS302ALK
Mechanical and electrical specifications
2
Mechanical and electrical specifications
2.1
Mechanical characteristics.
Table 2.
Mechanical characteristics(1)
All parameters are specified @ Vdd =3.3V, T = 25°C unless otherwise noted
Symbol
Ar
So
Parameter
Test Condition
Min.
Max.
Unit
±2.0
Acceleration range(3)
Sensitivity
Typ.(2)
(4)
0.415
0.440
g
0.465
V/g
SoDr
Sensitivity change Vs
Temperature
Delta from +25°C
Voff
Zero-g level(4)
T = 25°C
Zero-g level change
Vs Temperature
Delta from +25°C
±0.5
mg/°C
Non Linearity(5)
Best fit straight line
±0.5
% FS
±2
%
200
µg/ Hz
OffDr
NL
CrossAx
An
Vt
±0.01
Vdd/2-6%
Cross-Axis(6)
Acceleration Noise
Density
Self test output
voltage change(7),(8)
Fres
Sensing Element
Resonant
Frequency(9)
Top
Operating
Temperature Range
Wh
Product Weight
Vdd=3.3V
Vdd/2
%/°C
Vdd/2+6%
V
T = 25°C
Vdd=3.3V
X axis
+80
+220
mV
T = 25°C
Vdd=3.3V
Y axis
+80
+220
mV
T = 25°C
Vdd=3.3V
Z axis
+80
+220
mV
all axes
2.0
kHz
-40
+85
30
°C
mgram
1. The product is factory calibrated at 3.3V. The operational power supply range is specified in table 3. Since the device is
ratiometric 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 ratiometric to supply voltage
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. “Self test output voltage change” varies cubically with supply voltage
9. Minimum resonance frequency Fres=2.0kHz. Sensor bandwidth=1/(2*π*32kΩ*Cload)
5/14
Mechanical and electrical specifications
LIS302ALK
2.2
Electrical characteristics
Table 3.
Electrical characteristics(1)
All parameters are specified @ Vdd =3.3V, T=25°C unless otherwise noted
Symbol
Parameter
Test Condition
Vdd
Supply Voltage
Idd
Supply Current
mean value
PD pin connected to
GND
Supply Current in
Power Down Mode
PD pin connected to Vdd
IddPdn
Vst
Typ.(2)
Min.
Unit
V
0.65
mA
1
µA
Logic 0 level at Vdd=3.3V
0
0.8
V
Logic 1 level at Vdd=3.3V
2.0
Vdd
V
Self Test Input
Rout
Output impedance of
Voutx, Vouty, Voutz
Cload
Capacitive Load Drive
for Voutx, Vouty,
Voutz(3)
Ton
Turn-On Time at exit
from Power Down
mode
Top
Operating
Temperature Range
32
kΩ
2.5
Cload in μF
nF
160*Cload+0.3
-40
1. The product is factory calibrated at 3.3V.
2. Typical specifications are not guaranteed
3. Minimum resonance frequency Fres=2.0kHz. Device bandwidth=1/(2*π*32kΩ*Cload)
6/14
Max.
ms
+85
°C
LIS302ALK
2.3
Mechanical and electrical specifications
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.
Table 4.
Absolute maximum ratings
Symbol
Ratings
Vdd
Supply voltage
Vin
Input Voltage on Any Control pin (PD, ST)
Maximum Value
Unit
-0.3 to 6
V
-0.3 to Vdd +0.3
V
3000g for 0.5 ms
APOW
Acceleration (Any axis, Powered, Vdd=3.3V)
AUNP
Acceleration (Any axis, Not powered)
TSTG
Storage Temperature Range
10000g for 0.1 ms
3000g for 0.5 ms
ESD
10000g for 0.1 ms
Electrostatic Discharge Protection
-40 to +150
°C
2 (HBM)
KV
1.5 (CDM)
KV
200 (MM)
V
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
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 whereas
the Z axis will measure +1g. The output is ideally for a 3.3V powered sensor Vdd/2 =
1650mV. A deviation from ideal 0-g level (1650mV 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
7/14
Mechanical and electrical specifications
LIS302ALK
over lifetime. The Zero-g level tolerance describes the range of Zero-g levels of a population
of sensors.
Self Test allows to check the sensor functionality without moving it. 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 related to the selected full
scale and 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 Table 2, 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.
8/14
LIS302ALK
3
Functionality
Functionality
The LIS302ALK is an “piccolo” low-power, analog output three-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 fF 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 three 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 in 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.
9/14
Application hints
4
LIS302ALK
Application hints
Figure 3.
LIS302ALK electrical Connection
LIS302ALK
(top view)
Vdd
Vdd
GND
1
13
LIS302AL
GND
ST
100nF
Z
GND
10μF
X
Pin 1 indicator
GND
Y
GND
Optional
Vout z
Cload z
PD
6
1
DIRECTION OF THE
DETECTABLE
ACCELERATIONS
8
Optional
Vout Y
Cload y
Optional
Digital signals
Cload x
Vout X
Power supply decoupling capacitors (100nF ceramic or polyester + 10µF Aluminum) should
be placed as near as possible to the device (common design practice).
The LIS302ALK allows to band limit Voutx, Vouty and Voutz through the use of external
capacitors. The recommended frequency range spans from DC up to 2.0kHz. Capacitors
must be added at output pins to implement low-pass filtering for antialiasing and noise
reduction. The equation for the cut-off frequency (ft) of the external filters is:
1
f t = ---------------------------------------------------------------2π ⋅ R out ⋅ C load ( x, y, z )
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:
5μF
f t = ----------------------------------- [ Hz ]
C load ( x, y, z )
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, z) is required in any case.
10/14
LIS302ALK
Application hints
Table 5.
4.1
Filter capacitor selection, Cload (x,y,z)
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
Soldering information
The LGA package is compliant with the ECOPACK, RoHs and “Green” standard.It is
qualified for soldering heat resistance according to JEDEC J-STD-020C.
Pin1 indicator is electrically connected to pin 1. Leave pin 1 indicator unconnected during
soldering. Land pattern and soldering recommendations are available at www.st.com/mems.
4.2
Output response vs. orientation
Figure 4.
Output Response vs. Orientation
X=1.17V (-1g)
Y=1.65V (0g)
Z=1.65V (0g)
Bottom
X=1.65V (0g)
Y=2.13V (+1g)
Z=1.65V (0g)
TOP VIEW
X=2.13V (+1g)
Y=1.65V (0g)
Z=1.65V (0g)
Note:
X=1.65V (0g)
Y=1.17V (-1g)
Z=1.65V (0g)
Top
Top
X=1.65V (0g)
Y=1.65V (0g)
Z=1.17V (-1g)
X=1.65V (0g)
Y=1.65V (0g)
Bottom Z=2.13V (+1g)
Earth’s Surface
Figure 4 refers to LIS302ALK powered at 3.3V.
11/14
Package information
5
LIS302ALK
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.
Figure 5.
LGA 14: Mechanical Data & Package Dimensions
mm
inch
DIM.
MIN.
A1
TYP.
MAX.
0.920
1.000
0.0362 0.0394
0.700
0.0275
A2
MIN.
TYP.
MAX.
A3
0.180
0.220
0.260 0.0071 0.0087 0.0102
D1
2.850
3.000
3.150 0.1122 0.1181 0.1240
E1
4.850
5.000
5.150 0.1909 0.1968 0.2027
e
0.800
0.0315
d
0.300
0.0118
L1
4.000
0.1575
N
1.360
0.0535
N1
P1
1.200
0.965
0.975
OUTLINE AND
MECHANICAL DATA
0.0472
0.985 0.0380 0.0384 0.0386
P2
0.640
0.650
0.660 0.0252 0.0256 0.0260
T1
0.750
0.800
0.850 0.0295 0.0315 0.0335
T2
0.450
0.500
0.550 0.0177 0.0197 0.0217
R
1.200
1.600 0.0472
0.0630
h
0.150
0.0059
k
0.050
0.0020
i
0.100
0.0039
s
0.100
0.0039
LGA14 (3x5x0.92mm) Pitch 0.8mm
Land Grid Array Package
7773587 C
12/14
LIS302ALK
6
Revision history
Revision history
Table 6.
Document revision history
Date
Revision
30-Oct-2006
1
Changes
Initial release.
13/14
LIS302ALK
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