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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 2.2 Absolute maximum ratings.......................................................................................................5 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 4.2 4.3 4.4 4.5 Pin Description...........................................................................................................................7 Recommended circuit diagram ................................................................................................7 Recommended PWB layout ......................................................................................................8 Assembly instructions ..............................................................................................................9 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 5.4 5.5 5.6 5.7 Linearity ....................................................................................................................................11 Noise .........................................................................................................................................12 Bandwidth.................................................................................................................................13 Cross-axis sensitivity ..............................................................................................................13 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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1
1.1
General Description
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 Supply voltage Measuring range (selectable) Sensitivity (2g / 8g range) Interface Clock CMA3000-A01 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
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)
* 1 m drop on concrete may cause >>10000 g shock.
Value -0.3 to +3.6 -0.3 to (Vdd + 0.3) 2 -40 ... +125 -40 ... +85 < 10 000 Not allowed
Unit V V kV C C g
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 Symbol IPD VIH VIL Min -0.35 0.6*Dvio 0.4*Dvio Typ Max Unit A V V
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3 3.1
Package Characteristics Dimensions
The package dimensions are presented in Figure 2 below (dimensions in millimeters [mm] with 50 m tolerance).
Figure 2. Package dimensions in mm with 50 m 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. Table 4. CMA3000 pin descriptions. Pin # 1 2 3 4 5 6 7 8 Name VDD VSS VDD VOUTZ PD RANGE VOUTX VOUTY CMA3000-A01 Supply voltage Ground Supply voltage Output voltage Z-channel Power Down Acceleration Range Output voltage X-channel Output voltage Y-channel
Figure 4. CMA3000 pin numbers.
'0' = Active state '1' = Power Down '0' = 8g '1' = 2g
4.2
Recommended circuit diagram
1. Connect 100 nF SMD capacitor between both supply voltage pins and ground level. 2. Connect 1 F capacitor between each supply voltage and ground level. Recommended circuit diagram for the CMA3000 is shown in Figure 5 below.
VDD
1 2 3
VDD VSS VDD VOUTZ
VOUTY VOUTX RANGE PD
8 7 6 5
VOUTY VOUTX RANGE PD
VOUTZ 100n CL
4
CL
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 = 2 R C L 2 32k 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 Load capacitance, CL 47 nF 100 nF 220 nF 470 nF
4.3
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, [m]).
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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CMA3000-A0X Series
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 5.1
Data sheet references 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 Y X Earth's gravitation
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 OutputX-axisTempEr@T is sensor's X-axis temperature error in [mg] in temperature T, OutputX-axis@T is sensor's X-axis output reading [counts] in temperature T, OutputX-axis@T 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
Y-axis in +1 g position X Z
Z
X Earth's gravitation 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], OutputY-axis@+1g sensor's Y-axis output reading [counts] in +1 g position and OutputY-axis@-1g 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 SensY-axisTempEr@T is sensor's Y-axis sensitivity temperature error in [%] in temperature T, SensYaxis@T is sensor's measured Y-axis sensitivity [counts/g] at temperature T and SensY-axis@RT 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 Sensor's ideal output
Input acceleration [g] (centrifugal acceleration in parallel to CMA3000 measuring axis)
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 - Output@ acc Sens FS
100% ,
where LinErZ-axis@acc is sensor's Z-axis linearity error [%FS] on input acceleration acc, OutputZ-axis@acc is sensor's measured Z-axis output [counts] on input acceleration acc, Output@acc 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 Output@acc (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=
12 2 2 n X + nY + nZ , 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 Shaker movement in parallel to Z-axis Earth's gravitation
X
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
CrossY =
SYX + SYZ 100%, SY
2 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 Turn on time Time scale
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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7
Order Information
Order code
CMA3000-A01-1 CMA3000-A01-10 CMA3000-A01-30 CMA3000-A01 PWB CMA3000-D01DEMO
Description
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
Packing
T&R T&R T&R Bulk Bulk
Quantity
100 1000 3000 1 1
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Document Change Control
Version
0.1 0.2 0.3 0.4 0.5
Date
10-Sep07 11-Jan-08 14-Feb-08 01-Jul-08 10-Dec-08
Change Description
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: sales@vti.fi 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: sales.japan@vti.fi 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: sales.de@vti.fi 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: sales@vtitechnologies.com
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: sales.china@vti.fi
To find out your local sales representative visit www.vti.fi
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