VTI CMA3000

Doc.Nr. 8282100.05
Product Family Specification
CMA3000-A0X Series
3-axis accelerometer
CMA3000-A0X Series
TABLE OF CONTENTS
1 General Description ............................................................................................................. 4
1.1
Introduction ................................................................................................................................4
1.2 Functional Description ..............................................................................................................4
1.2.1 Sensing element..................................................................................................................4
1.2.2 Interface IC...........................................................................................................................4
1.2.3 Factory calibration ..............................................................................................................4
1.2.4 Supported features .............................................................................................................5
2 Electrical Characteristics .................................................................................................... 5
2.1
Absolute maximum ratings.......................................................................................................5
2.2
Power Supply .............................................................................................................................5
2.3 Digital I/O Specification.............................................................................................................5
2.3.1 Digital I/O DC characteristics .............................................................................................5
3 Package Characteristics...................................................................................................... 6
3.1
Dimensions.................................................................................................................................6
4 Application information ....................................................................................................... 7
4.1
Pin Description...........................................................................................................................7
4.2
Recommended circuit diagram ................................................................................................7
4.3
Recommended PWB layout ......................................................................................................8
4.4
Assembly instructions ..............................................................................................................9
4.5
Tape and reel specifications.....................................................................................................9
5 Data sheet references ........................................................................................................ 10
5.1 Offset.........................................................................................................................................10
5.1.1 Offset calibration error .....................................................................................................10
5.1.2 Offset temperature error...................................................................................................10
5.2 Sensitivity .................................................................................................................................10
5.2.1 Sensitivity calibration error..............................................................................................11
5.2.2 Sensitivity temperature error ...........................................................................................11
5.3
Linearity ....................................................................................................................................11
5.4
Noise .........................................................................................................................................12
5.5
Bandwidth.................................................................................................................................13
5.6
Cross-axis sensitivity ..............................................................................................................13
5.7
Turn-on time .............................................................................................................................14
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6 Known issues ..................................................................................................................... 14
6.1
Sensing element's bandwidth is lower than the target ........................................................14
7 Order Information............................................................................................................... 15
8 Document Change Control................................................................................................ 16
9 Contact Information ........................................................................................................... 17
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CMA3000-A0X Series
1
General Description
1.1
Introduction
CMA3000-A0X is a three axis accelerometer family targeted for high volume products requiring
small size, low price and low power consumption. It consists of a 3D-MEMS sensing element and a
signal conditioning ASIC in a wafer level package.
Both block diagram of CMA3000-A0X is shown in Figure 1 below.
X-out
C/V
Analog
calibration
&
low-pass
filtering
Y-out
Z-out
Oscillator
&
clock
Reference
NonVolatile
Memory
Control
Range
PD
Figure 1. CMA3000-A0X block diagram with analog interface
This document, no. 82821000, describes the product specification (e.g. operation modes, electrical
properties and application information) for the CMA3000-A0X family. The specification for an
individual sensor is available in the corresponding data sheet.
1.2
1.2.1
Functional Description
Sensing element
The sensing element is manufactured using the proprietary bulk 3D-MEMS process, which enables
robust, stable and low noise & power capacitive sensors.
The sensing element consists of three acceleration sensitive masses. Acceleration will cause a
capacitance change that will be then converted into a voltage change in the signal conditioning
ASIC.
1.2.2
Interface IC
CMA3000 includes an internal oscillator, reference and non-volatile memory that enable the
sensor's autonomous operation within a system.
The sensing element is interfaced via a capacitance-to-voltage (CV) converter. Following
calibration in the analog domain, the signal is filtered and buffered.
In active mode analog voltages representing the measured acceleration are available X-, Y-, Z-out
pins. Power Down and measurement range can be selected using external Range ('0'=8g, '1'=2g)
and PD ( '0' =Active, '1'= Power Down ) pins.
1.2.3
Factory calibration
Sensors are factory calibrated. Trimmed parameters are gain, offset, internal current reference and
the frequency of the internal oscillator. Calibration parameters will be read automatically from the
internal non-volatile memory during sensor startup.
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1.2.4
Supported features
Supported features are listed in Table 1 below.
Table 1. CMA3000-A0X devices’ summary.
Features
CMA3000-A01
Supply voltage
Measuring range (selectable)
Sensitivity (2g / 8g range)
1.7 V – 3.6 V
±2 g, ±8 g
0.167*Vdd / 0.042*Vdd V/g
3 analog output voltages, 32 kOhm output impedance
Extenal pins for power down and measurement range
Internal
Interface
Clock
2
Electrical Characteristics
All voltages are reference to ground. Currents flowing into the circuit have positive values.
2.1
Absolute maximum ratings
The absolute maximum ratings of the CMA3000 are presented in Table 2 below.
Table 2. Absolute maximum ratings of the CMA3000
Parameter
Supply voltage (Vdd)
Voltage at input / output pins
ESD (Human body model)
Storage temperature
Storage / operating temperature
Mechanical shock *
Exposure to ultrasonic energy
(e.g. ultra sonic washing or
welding)
Value
-0.3 to +3.6
-0.3 to (Vdd + 0.3)
±2
-40 ... +125
-40 ... +85
< 10 000
Unit
V
V
kV
°C
°C
g
Not allowed
* 1 m drop on concrete may cause >>10000 g shock.
2.2
Power Supply
Please refer to the corresponding product datasheet.
2.3
2.3.1
Digital I/O Specification
Digital I/O DC characteristics
Table 3. DC characteristics of digital I/O pins.
No. Parameter
Conditions
Input: PD, RANGE with pull up
Pull up current: PD,
VIN = 0 V
1
RANGE
Input high voltage
2
Input low voltage
3
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Symbol
Min
Typ
Max
IPD
-0.35
µA
VIH
VIL
0.6*Dvio
V
V
0.4*Dvio
Unit
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CMA3000-A0X Series
3
3.1
Package Characteristics
Dimensions
The package dimensions are presented in Figure 2 below (dimensions in millimeters [mm] with
±50 µm tolerance).
Figure 2. Package dimensions in mm with ±50 µm tolerance for reference only. Please check the
corresponding data sheet for details.
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4
4.1
Application information
Pin Description
CMA3000 pin numbers are presented in Figure 4 below and pin descriptions in Table 4.
Z
X
Y
Figure 3. CMA3000 sensing directions.
Figure 4. CMA3000 pin numbers.
Table 4. CMA3000 pin descriptions.
4.2
Pin #
1
2
3
4
5
Name
VDD
VSS
VDD
VOUTZ
PD
CMA3000-A01
Supply voltage
Ground
Supply voltage
Output voltage Z-channel
Power Down
6
RANGE
Acceleration Range
7
8
VOUTX
VOUTY
Output voltage X-channel
Output voltage Y-channel
'0' = Active state
'1' = Power Down
'0' = 8g
'1' = 2g
Recommended circuit diagram
1. Connect 100 nF SMD capacitor between both supply voltage pins and ground level.
2. Connect 1 µF capacitor between each supply voltage and ground level.
Recommended circuit diagram for the CMA3000 is shown in Figure 5 below.
1
VDD
2
3
4
VOUTZ
100n
VDD
VOUTY
VSS
VOUTX
VDD
RANGE
VOUTZ
PD
8
VOUTY
7
VOUTX
6
RANGE
5
CL
CL
PD
CL
Figure 5. Recommended circuit diagram for CMA3000-A0X
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Please note that CMA3000-A0X has internal 32kOhm resistors in series with all analog outputs.
Due to this internal resistor the resulting signal bandwidth of CMA3000 will be a function of the CL
as follows:
f −3dB =
1
1
=
2π ⋅ R ⋅ C L 2π ⋅ 32kΩ ⋅ C L
,
where CL is the load capacitance presented in Figure 5. Some example signal bandwidths are
presented in Table 5 below.
Table 5. CMA3000 pin descriptions.
Signal bandwitdh,
-3dB cut off frequency
106 Hz
50 Hz
23 Hz
11 Hz
4.3
Load capacitance, CL
47 nF
100 nF
220 nF
470 nF
Recommended PWB layout
Below are general PWB layout recommendations for CMA3000 products (refer to Figure 5 and
Figure 6):
1. Locate 100 nF SMD capacitors right next to the CMA3000 package.
2. Use double sided PWB, connect the bottom side plane to GND.
Recommended PWB pad layout for CMA3000 is presented in Figure 6 below (dimensions in
micrometers, [µm]).
Figure 6. Recommended PWB pad layout for CMA3000.
Recommended PWB layout for the CMA3000-A0X is presented in Figure 7 below (circuit diagram
presented in Figure 5 above).
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Note the symmetrical ground
plane under the component.
Figure 7. Recommended PWB layout for CMA3000-A0X (not actual size, for reference
only).
4.4
Assembly instructions
The Moisture Sensitivity Level (MSL) of the CMA3000 component is 3 according to the IPC/JEDEC
J-STD-020D. Please refer to the document TN68_CMA3000_Assembly_Instructions for more
detailed information of CMA3000 assembly.
4.5
Tape and reel specifications
Please refer to the document TN68_CMA3000_Assembly_Instructions for tape and reel
specifications.
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5
Data sheet references
5.1
Offset
CMA3000's offset will be calibrated in X = 0 g, Y = 0 g, and Z = +1 g (Z measuring axis is parallel to
earth’s gravitation) position, see Figure 8.
Z-axis in +1 g
position
Earth’s
gravitation
Y
X
Pin #1
Figure 8. CMA3000 offset (0 g) position.
5.1.1
Offset calibration error
Offset calibration error is the difference between the sensor's actual output reading and the nominal
output reading in calibration conditions. Error is calculated by
Equation 1
Offset X −axisCalibEr =
Output X −axis − Output
⋅ 1000 ,
Sens
where OutputX-axisCalibEr is sensor’s X-axis calibration error in [mg], OutputX-axis is sensor’s X-axis
output reading [counts], Output is sensor’s nominal output in 0 g position and Sens sensor’s nominal
sensitivity [counts/g].
5.1.2
Offset temperature error
Offset temperature error is the difference between the sensor's output reading in different
temperatures and the sensor’s calibrated offset value at room temperature. Error is calculated by
Equation 2
Offset X − axisTempEr @ T =
Output X − axis @ T − Output X − axis @ RT
Sens
⋅1000 ,
where [email protected] is sensor’s X-axis temperature error in [mg] in temperature T, [email protected]
is sensor’s X-axis output reading [counts] in temperature T, [email protected] X-axis output reading
[counts] at room temperature RT and Sens sensor’s nominal sensitivity [counts/g]. Sensor is in 0 g
position for every measurement point.
5.2
Sensitivity
During sensitivity calibration, the sensor is placed in ±1 g positions having one of the sensor’s
measuring axis at a time parallel to the earth’s gravitation, see Figure 9.
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Pin #1
Z
Y-axis in +1 g
position
X
Earth’s
gravitation
X
Z
Y-axis in -1 g
position
Pin #1
Figure 9. CMA3000 positions for Y-axis sensitivity measurement.
Sensitivity is calculated by
Equation 3
SensY − axis =
OutputY − axis @ +1g − OutputY − axis @ −1g
2g
,
where SensY-axis is sensor’s Y-axis sensitivity in [counts/g], [email protected]+1g sensor’s Y-axis output
reading [counts] in +1 g position and [email protected] is sensor’s Y-axis output reading [counts] in -1 g
position.
5.2.1
Sensitivity calibration error
Sensitivity calibration error is the difference between sensor’s measured sensitivity and the nominal
sensitivity at room temperature conditions. Error is calculated by
Equation 4
SensY − axisCalibEr =
SensY − axis − Sens
⋅100% ,
Sens
where SensY-axisCalibEr is sensor’s Y-axis sensitivity calibration error in [%], SensY-axis sensor’s Y-axis
sensitivity [counts/g] at room temperature conditions and Sens is sensor’s nominal sensitivity
[counts/g].
5.2.2
Sensitivity temperature error
Sensitivity temperature error is the difference between sensor’s sensitivity at different temperatures
and the calibrated sensitivity. Error is calculated by
Equation 5
SensY − axisTempEr @T =
SensY − axis @T − SensY − axis @ RT
SensY − axis @ RT
⋅100% ,
where [email protected] is sensor’s Y-axis sensitivity temperature error in [%] in temperature T, [email protected] is sensor’s measured Y-axis sensitivity [counts/g] at temperature T and [email protected] is sensor’s
measured Y-axis sensitivity [counts/g] at room temperature RT.
5.3
Linearity
The needed accurate input acceleration in linearity characterization is generated using centrifugal
force in centrifuge, see Figure 10. The RPM of the centrifuge is sweeped so that wanted input
acceleration values are applied in parallel to the sensor’s measuring axis.
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X
Z
Centrifugal
acceleration
for Z-axis
Y
Pin #1
Figure 10. Centrifugal acceleration applied for CMA3000 Z-axis.
Linearity error is the deviation from the best bit straight line. See Figure 11.
Acceleration reading
from CMA3000 [g]
CMA3000 linearity
error in [g] at input
acceleration acc
-FS
+FS
acc
CMA3000 output
readings
Input acceleration [g] (centrifugal
acceleration in parallel to
CMA3000 measuring axis)
Sensor’s ideal
output
Possible offset error is not
included into linearity error
Figure 11. CMA3000’s linearity error at input acceleration acc.
Linearity error is calculated by
Equation 6
LinErZ −axis @ acc =
OutputZ −axis @ acc − [email protected] acc
Sens ⋅ FS
⋅100% ,
where [email protected] is sensor’s Z-axis linearity error [%FS] on input acceleration acc, [email protected]
is sensor’s measured Z-axis output [counts] on input acceleration acc, [email protected] is sensor’s
nominal output [counts] on input acceleration acc, Sens is sensor’s nominal sensitivity [counts/g] and
FS is sensor’s full scale measuring range [g] (for example for CMA3000-A01 with ±2g setting →
FS = 2 g).
Sensor’s ideal output [email protected] (in Equation 6) is calculated by fitting a straight line to measured
accelerations from –FS to FS.
5.4
Noise
Output noise nX, nY and nZ in X,Y and Z directions is the measured standard deviation of the output
values when the sensor is in 0 g position at room temperature. Average noise/axis is calculated by
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Equation 7
n=
(
)
1 2
n X + nY2 + nZ2 ,
3
where n is sensor’s noise [g] per axis, nX is sensor’s X-axis noise [g], nY is sensor’s Y-axis noise [g]
and nZ is sensor’s Z-axis noise [g].
CMA3000 demo-kit design can be used as a reference design for noise measurements, refer to
“CMA3000 DEMO KIT User Manual TBD”.
5.5
Bandwidth
Signal bandwidth is measured in a shaker by sweeping the piston movement frequency with
constant amplitude (Figure 12).
Z
Y
X
Shaker
movement
in parallel
to Z-axis
Earth’s
gravitation
Pin #1
Figure 12. CMA3000 movement in Z-axis bandwidth measurement.
5.6
Cross-axis sensitivity
Cross-axis sensitivity is sum of the alignment and the inherent sensitivity errors. Cross-axis
sensitivity of one axis is a geometric sum of the sensitivities in two perpendicular directions.
Cross-axis sensitivity [%] of X-axis is given by
Equation 8
S + S XZ
⋅100%,
Cross X = ± XY
SX
2
2
where SXY is X-axis sensitivity to Y-axis acceleration [Count/g], SXZ is X-axis sensitivity to Z-axis
acceleration [Count/g] and SX is sensitivity of X-axis [Count/g].
Cross-axis sensitivity [%] of Y-axis is given by
Equation 9
SYX + SYZ
⋅100%,
SY
2
CrossY = ±
2
where SYX is Y-axis sensitivity to X-axis acceleration [Count/g], SYZ is Y-axis sensitivity to Z-axis
acceleration [Count/g] and SY is sensitivity of Y-axis [Count/g].
Cross-axis sensitivity [%] of Z-axis is given by
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Equation 10
S + S ZY
⋅ 100%,
CrossZ = ± ZX
SZ
2
2
where SZX is Z-axis sensitivity to X-axis acceleration [Count/g], SZY is Z-axis sensitivity to Y-axis
acceleration [Count/g] and SZ is sensitivity of Z-axis [Count/g].
Cross-axis sensitivity of CMA3000 family is measured in centrifuge over specified measurement
range during qualification. Correct mounting position of component is important during the
measurement of cross-axis sensitivity.
5.7
Turn-on time
Turn-on time is the time when the last of one X, Y, Z axis output readings stabilizes into its final
value after XRESET is pulled high. The final value limits in turn-on time measurements is defined to
be ±1 % of the sensor’s full scale measuring range (for example for CMA3000-A01 ±2g →
FS = 2 g). Turn-on time definition for Z-axis is presented in Figure 13 below.
Acceleration
Supply voltage reaches the
minimum required level
→ CMA3000 starts
CMA3000 output
inside ±1% FS
limits
CMA3000
Z-axis output
Time scale
Turn on time
Figure 13. Turn-on time definition for one axis.
6
6.1
Known issues
Sensing element's bandwidth is lower than the target
Due to design issue (to be corrected) sensing element's mechanical bandwidth is lower than the
target. As a result, without external load capacitors the bandwidth to X and Z direction is typically
90 Hz and to Y direction typically 150 Hz.
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Order Information
Order code
Description
CMA3000-A01-1
CMA3000-A01-10
CMA3000-A01-30
CMA3000-A01 PWB
CMA3000-D01DEMO
3-Axis accelerometer with SPI&I2C interface, +/- 2/8g, 100 pcs
3-Axis accelerometer with SPI&I2C interface, +/- 2/8g, 1000 pcs
3-Axis accelerometer with SPI&I2C interface, +/- 2/8g, 3000 pcs
PWB assy 3-Axis accelerometer with SPI&I2C interface, +/- 2/8g
CMA3000-D01 DEMOKIT
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Packing
T&R
T&R
T&R
Bulk
Bulk
Quantity
100
1000
3000
1
1
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8
Document Change Control
Version
Date
Change Description
0.1
0.2
0.3
0.4
0.5
10-Sep07
11-Jan-08
14-Feb-08
01-Jul-08
10-Dec-08
Initial draft.
Major update.
Minor updates, corrections
Table 1 and Figure 2 updated
Figure 2 updated, section 6 added.
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Contact Information
Finland
(head office)
VTI Technologies Oy
P.O. Box 27
Myllynkivenkuja 6
FI-01621 Vantaa
Finland
Tel. +358 9 879 181
Fax +358 9 8791 8791
E-mail: [email protected]
Germany
VTI Technologies Oy
Branch Office Frankfurt
Rennbahnstrasse 72-74
D-60528 Frankfurt am Main,
Germany
Tel. +49 69 6786 880
Fax +49 69 6786 8829
E-mail: [email protected]
Japan
VTI Technologies Oy
Tokyo Office
Tokyo-to, Minato-ku 2-7-16
Bureau Toranomon 401
105-0001
Japan
Tel. +81 3 6277 6618
Fax +81 3 6277 6619
E-mail: [email protected]
China
VTI Technologies Shanghai Office
6th floor, Room 618
780 Cailun Lu
Pudong New Area
201203 Shanghai
P.R. China
Tel. +86 21 5132 0417
Fax +86 21 513 20 416
E-mail: [email protected]
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USA
VTI Technologies, Inc.
One Park Lane Blvd.
Suite 804 - East Tower
Dearborn, MI 48126
USA
Tel. +1 313 425 0850
Fax +1 313 425 0860
E-mail: [email protected]
To find out your local sales
representative visit www.vti.fi
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