MXA2500ML [ETC]
Improved, Ultra Low Noise ±1.7 g Dual Axis Accelerometer with Absolute Outputs; 改善，超低噪音±1.7 g两轴加速度计输出的绝对
| 型号： | MXA2500ML |
| 厂家： | 
ETC |
| 描述： | Improved, Ultra Low Noise ±1.7 g Dual Axis Accelerometer with Absolute Outputs |
| 文件： | 总8页 (文件大小：335K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Improved, Ultra Low Noise ±1.7 g
Dual Axis Accelerometer with
Absolute Outputs
MXA2500G/M
FEATURES
Resolution better than 1 milli-g
Sck
(optional)
Internal
Oscillator
Temperature
Sensor
TOUT
Dual axis accelerometer fabricated on a monolithic CMOS IC
On chip mixed mode signal processing
No moving parts
Voltage
Reference
VREF
CLK
50,000 g shock survival rating
Continous
Self Test
Heater
Control
17 Hz bandwidth expandable to >160 Hz
3.0V to 5.25V single supply continuous operation
Continuous self test
Independent axis programmability (special order)
Internal Sensitivity Compensated
Low Pass
Filter
X axis
AOUTX
Factory Adjust
Offset & Gain
APPLICATIONS
Automotive – Vehicle Security/Vehicle Stability control/
Headlight Angle Control/Tilt Sensing
Security – Gas Line/Elevator/Fatigue Sensing/Computer Security
Information Appliances – Computer Peripherals/PDA’s/Mouse
Smart Pens/Cell Phones
Low Pass
Filter
Y axis
AOUTY
2-AXIS
SENSOR
VDD
Gnd
VDA
MXA2500G/M FUNCTIONAL BLOCK DIAGRAM
Gaming – Joystick/RF Interface/Menu Selection/Tilt Sensing
GPS – Electronic compass tilt correction
Consumer – LCD projectors, pedometers, blood pressure
Monitor, digital cameras
GENERAL DESCRIPTION
The MXA2500G/M is a low cost, dual axis accelerometer
fabricated on a standard, submicron CMOS process. It is a
complete sensing system with on-chip mixed mode signal
processing. The MXA2500G/M measures acceleration
with a full-scale range of ±1.7g and a sensitivity of
500mV/g @5V at 25°C. It can measure both dynamic
acceleration (e.g. vibration) and static acceleration (e.g.
gravity). The MXA2500G/M design is based on heat
convection and requires no solid proof mass. This
eliminates stiction and particle problems associated with
competitive devices and provides shock survival of 50,000
g, leading to significantly lower failure rate and lower loss
due to handling during assembly.
The MXA2500G/M provides two absolute analog outputs.
The typical noise floor is 0.2 mg/ Hz allowing signals
below 1 milli-g to be resolved at 1 Hz bandwidth. The
3dB rolloff of the device occurs at 17 Hz but is expandable
to >160 Hz (reference Application Note AN-00MX-003).
The MXA2500G/M is packaged in a hermetically sealed
LCC surface mount package (5 mm x 5 mm x 2 mm height)
and is operational over a -40°C to 105°C(M) and 0°C to
70°C(G) temperature range.
Information furnished by MEMSIC is believed to be accurate and reliable.
However, no responsibility is assumed by MEMSIC for its use, nor for any
infringements of patents or other rights of third parties which may result from
its use. No license is granted by implication or otherwise under any patent or
patent rights of MEMSIC.
MEMSIC, Inc.
800 Turnpike St., Suite 202, North Andover, MA 01845
Tel: 978.738.0900
www.memsic.com
Fax: 978.738.0196
MEMSIC MXA2500G/M Rev. E
Page 1 of 8
1/19/2005
MXA2500G/M SPECIFICATIONS (Measurements @ 25°C, Acceleration = 0 g unless otherwise noted; VDD, VDA = 5.0V unless
otherwise specified)
MXA2500G
Typ
MXA2500M
Typ
Parameter
Conditions
Min
Max
Min
Max
Units
SENSOR INPUT
Each Axis
Measurement Range1
g
±1.7
±1.7
Nonlinearity
Best fit straight line
X Sensor to Y Sensor
0.5
1.0
0.5
1.0
% of FS
degrees
%
Alignment Error2
Transverse Sensitivity3
±1.0
±2.0
±1.0
±2.0
SENSITIVITY
Each Axis
Sensitivity, Analog Outputs at
pins
475
-10
500
525
+8
475
-25
500
525
+8
mV/g
5
A
OUTX and AOUTY
Change over Temperature
ZERO g BIAS LEVEL
0 g Offset5
%
Each Axis
-0.1
0.0
1.25
±1.5
±0.75
+0.1
1.30
-0.1
0.0
1.25
±1.5
±0.75
+0.1
1.30
g
V
mg/°C
mV/°C
0 g Voltage5
1.20
1.20
0 g Offset over Temperature
Based on 500 mV/g
NOISE PERFORMANCE
Noise Density, rms
Without frequency
compensation
0.2
0.4
19
0.2
0.4 mg/ Hz
FREQUENCY RESPONSE
3dB Bandwidth - uncompensated
3dB Bandwidth – compensated4
TEMPERATURE OUTPUT
Tout Voltage
15
17
15
17
19
Hz
Hz
>160
>160
1.15
4.6
1.25
5.0
1.35
5.4
1.15
4.6
1.25
5.0
1.35
5.4
V
Sensitivity
mV/°K
VOLTAGE REFERENCE
VRef
@3.0V-5.25V supply
Source
2.4
2.5
0.1
2.65
100
2.4
2.5
0.1
2.65
100
V
mV/°C
µA
Change over Temperature
Current Drive Capability
SELF TEST
Continuous Voltage at AOUTX
,
@5.0V Supply, output
rails to
AOUTY under Failure
5.0
3.0
5.0
3.0
V
V
supply voltage
@3.0V Supply, output
rails to
Continuous Voltage at AOUTX
,
AOUTY under Failure
supply voltage
AOUTX and AOUTY OUTPUTS
Normal Output Range
@5.0V Supply
@3.0V Supply
0.1
0.1
4.9
2.9
100
0.1
0.1
4.9
2.9
100
V
V
µA
Current
Source or sink, @
3.0V-5.25V supply
@5.0V Supply
Turn-On Time6
160
300
160
300
mS
mS
@3.0V Supply
POWER SUPPLY
Operating Voltage Range
Supply Current
3.0
2.5
3.0
5.25
3.9
3.0
2.5
3.0
5.25
3.9
V
@ 5.0V
@ 3.0V
3.1
3.8
3.1
3.8
mA
mA
Supply Current5
4.6
4.6
TEMPERATURE RANGE
Operating Range
0
+70
-40
+105
°C
5
The device operates over a 3.0V to 5.25V supply range. Please note that sensitivity and
zero g bias level will be slightly different at 3.0V operation. For devices to be operated at
3.0V in production, they can be trimmed at the factory specifically for this lower supply
voltage operation, in which case the sensitivity and zero g bias level specifications on this
page will be met. Please contact the factory for specially trimmed devices for low supply
voltage operation.
NOTES
1
Guaranteed by measurement of initial offset and sensitivity.
Alignment error is specified as the angle between the true and indicated axis of
2
sensitivity.
3
Transverse sensitivity is the algebraic sum of the alignment and the inherent sensitivity
5
errors.
Output settled to within ±17mg.
4
External circuitry is required to extend the 3dB bandwidth (ref. Application Note: AN-
00MX-003)
MEMSIC MXA2500G/M Rev. E
Page 2 of 8
1/19/2005
8
4
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (VDD, VDA) ………………...-0.5 to +7.0V
Storage Temperature ……….…………-65°C to +150°C
Acceleration, constant…………….……………..50,000 g
Shock (Powered) , Half Sine (shock rating limited by test
equipment, virtually unlimited by design)
1
2
3
7
6
5
X
+ g
Level (g)
3000
2000
1000
700
Duration(ms)
Y
+ g
T o p V iew
0.5
1.0
2.0
3.0
5.0
Figure 1: Note - The MEMSIC logo’s arrow indicates the +X
sensing direction of the device. The +Y sensing direction is
rotated 90° away from the +X direction following the right-hand
rule. Small circle indicates pin one(1).
500
*Stresses above those listed under Absolute Maximum Ratings may cause permanent
damage to the device. This is a stress rating only; the functional operation of the
device at these or any other conditions above those indicated in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
Package Characteristics
Package
Device Weight
θJA
θJC
LCC-8
< 1 gram
110°C/W 22°C/W
Pin Description: LCC-8 Package
Pin
1
Name
TOUT
AOUTY
Gnd
Description
THEORY OF OPERATION
Temperature (Analog Voltage)
Y-Axis Acceleration Signal
Ground
The MEMSIC device is a complete dual-axis acceleration
measurement system fabricated on a monolithic CMOS IC
process. The device operation is based on heat transfer by
natural convection and operates like other accelerometers
having a proof mass. The proof mass in the MEMSIC
sensor is a gas.
2
3
4
VDA
Analog Supply Voltage
X-Axis Acceleration Signal
2.5V Reference
Optional External Clock
Digital Supply Voltage
5
AOUTX
Vref
Sck
VDD
6
7
8
A single heat source, centered in the silicon chip is
suspended across a cavity. Equally spaced
Ordering Guide
Model
MXA2500GL
aluminum/polysilicon thermopiles (groups of
Package Style
Temperature Range
0 to 70°C
thermocouples) are located equidistantly on all four sides of
the heat source (dual axis). Under zero acceleration, a
temperature gradient is symmetrical about the heat source,
so that the temperature is the same at all four thermopiles,
causing them to output the same voltage.
LCC8
RoHS compliant
MXA2500GF
MXA2500ML
LCC8, Pb-free
0 to 70°C
-40 to 105°C
LCC8
RoHS compliant
MXA2500MF
All parts are shipped in tape and reel packaging.
Caution: ESD (electrostatic discharge) sensitive device.
LCC8, Pb-free
-40 to 105°C
Acceleration in any direction will disturb the temperature
profile, due to free convection heat transfer, causing it to be
asymmetrical. The temperature, and hence voltage output
of the four thermopiles will then be different. The
differential voltage at the thermopile outputs is directly
proportional to the acceleration. There are two identical
acceleration signal paths on the accelerometer, one to
measure acceleration in the x-axis and one to measure
acceleration in the y-axis. Please visit the MEMSIC
website at www.memsic.com for a picture/graphic
description of the free convection heat transfer principle
MEMSIC MXA2500G/M Rev. E
Page 3 of 8
1/19/2005
TYPICAL CHARACTERISTICS, % OF UNITS ( @ 25°C, Vdd = 5V , unless specified)
25%
20%
15%
10%
5%
60%
50%
40%
30%
20%
10%
0%
0%
Graph 1. Distribution of Tout (Volts)
Graph 2. Distribution of Vref (Volts)
Graph 3. Distribution of Idd (mA)
Graph 5. Distribution of 0g Offset AOUTX (Volts)
25%
20%
15%
10%
5%
60%
50%
40%
30%
20%
10%
0%
0%
Graph 6. Distribution of 0g Offset AOUTY (Volts)
35%
30%
25%
20%
15%
10%
5%
25%
20%
15%
10%
5%
0%
0%
Graph 7. Distribution of AOUTX Sensitivity (mV/g)
25%
20%
15%
10%
5%
40%
30%
20%
10%
0%
0%
Graph 4. Distribution of Freq. Resp. (Hz)
Graph 8. Distribution of AOUTY Sensitivity (mV/g)
MEMSIC MXA2500G/M Rev. E
Page 4 of 8
1/19/2005
TYPICAL CHARACTERISTICS OVER TEMPERATURE ( 0°C to 70°C, Vdd = 5V , unless specified)
40%
35%
30%
25%
20%
15%
10%
5%
100
80
60
40
20
0
-20
-40
-60
-80
-100
0%
milli-g / °C
0°C 10°C 20°C 30°C 40°C 50°C 60°C 70°C
Graph 9. Distribution of AOUTX 0g offset over temperature
Graph 12. Examples of AOUTY 0g offset vs. temperature
8%
40%
35%
30%
25%
20%
15%
10%
5%
6%
4%
2%
0%
-2%
-4%
-6%
0%
-8%
-10%
milli-g / °C
0°C 10°C 20°C 30°C 40°C 50°C 60°C 70°C
Graph 10. Distribution of AOUTY 0g offset over temperature
Graph 13. Examples of AOUTX Sensitivity change over temperature
100
8%
80
6%
60
4%
40
2%
20
0%
0
-2%
-20
-4%
-40
-6%
-60
-8%
-80
-10%
-100
0°C 10°C 20°C 30°C 40°C 50°C 60°C 70°C
0°C 10°C 20°C 30°C 40°C 50°C 60°C 70°C
Graph 11. Examples of AOUTX 0g offset vs. temperature
Graph 14. Examples of AOUTY Sensitivity change over temperature
MEMSIC MXA2500G/M Rev. E
Page 5 of 8
1/19/2005
the force of gravity (perpendicular to the Earth’s surface), it is
least sensitive to changes in tilt.
MXA2500G/M PIN DESCRIPTIONS
VDD – This is the supply input for the digital circuits and the
sensor heater in the accelerometer. The DC voltage should be
between 3.0 and 5.25 volts. Refer to the section on PCB layout
and fabrication suggestions for guidance on external parts and
connections recommended.
Table 1 and Figure 2 help illustrate the output changes in the
X- and Y-axes as the unit is tilted from +90° to 0°. Notice that
when one axis has a small change in output per degree of tilt
(in mg), the second axis has a large change in output per
degree of tilt. The complementary nature of these two signals
permits low cost accurate tilt sensing to be achieved with the
MEMSIC device (reference application note AN-00MX-007).
VDA – This is the power supply input for the analog amplifiers
in the accelerometer. Refer to the section on PCB layout and
fabrication suggestions for guidance on external parts and
connections recommended.
X
+900
Gnd – This is the ground pin for the accelerometer.
gravity
AOUTX – This pin is the output of the x-axis acceleration sensor.
The user should ensure the load impedance is sufficiently high
as to not source/sink >100µA. While the sensitivity of this axis
has been programmed at the factory to be the same as the
sensitivity for the y-axis, the accelerometer can be programmed
for non-equal sensitivities on the x- and y-axes. Contact the
factory for additional information on this feature.
00
Y
Top View
Figure 2: Accelerometer Position Relative to Gravity
X-Axis
Y-Axis
Change
AOUTY – This pin is the output of the y-axis acceleration sensor.
The user should ensure the load impedance is sufficiently high
as to not source/sink >100µA. While the sensitivity of this axis
has been programmed at the factory to be the same as the
sensitivity for the x-axis, the accelerometer can be programmed
for non-equal sensitivities on the x- and y-axes. Contact the
factory for additional information on this feature.
X-Axis
Orientation
Change
To Earth’s
X Output
per deg.
of tilt
(mg)
0.15
Y Output
per deg.
of tilt
(mg)
17.45
17.37
17.16
16.35
15.04
12.23
8.59
Surface
(deg.)
90
(g)
(g)
1.000
0.996
0.985
0.940
0.866
0.707
0.500
0.342
0.174
0.087
0.000
0.000
0.087
0.174
0.342
0.500
0.707
0.866
0.940
0.985
0.996
1.000
85
1.37
80
2.88
70
5.86
TOUT – This pin is the buffered output of the temperature
sensor. The analog voltage at TOUT is an indication of the die
temperature. This voltage is useful as a differential
measurement of temperature from ambient and not as an
absolute measurement of temperature
60
8.59
45
12.23
15.04
16.35
17.16
17.37
17.45
30
20
5.86
10
2.88
5
1.37
Sck – The standard product is delivered with an internal clock
option (800kHz). This pin should be grounded when
operating with the internal clock. An external clock option
can be special ordered from the factory allowing the user to
input a clock signal between 400kHz and 1.6MHz.
0
0.15
Table 1: Changes in Tilt for X- and Y-Axes
Resolution: The accelerometer resolution is limited by noise.
The output noise will vary with the measurement bandwidth.
With the reduction of the bandwidth, by applying an external
low pass filter, the output noise drops. Reduction of bandwidth
will improve the signal to noise ratio and the resolution. The
output noise scales directly with the square root of the
measurement bandwidth. The maximum amplitude of the noise,
its peak- to- peak value, approximately defines the worst case
resolution of the measurement. With a simple RC low pass
filter, the rms noise is calculated as follows:
Vref – A reference voltage is available from this pin. It is set at
2.50V typical and has 100µA of drive capability.
DISCUSSION OF TILT APPLICATIONS AND
RESOLUTION
Tilt Applications: One of the most popular applications of the
MEMSIC accelerometer product line is in tilt/inclination
measurement. An accelerometer uses the force of gravity as an
input to determine the inclination angle of an object.
Noise (mg rms) = Noise(mg/ Hz ) *
(Bandwidth(Hz)*1.6)
The peak-to-peak noise is approximately equal to 6.6 times the
rms value (for an average uncertainty of 0.1%).
A MEMSIC accelerometer is most sensitive to changes in
position, or tilt, when the accelerometer’s sensitive axis is
perpendicular to the force of gravity, or parallel to the Earth’s
surface. Similarly, when the accelerometer’s axis is parallel to
MEMSIC MXA2500G/M Rev. E
Page 6 of 8
1/19/2005
EXTERNAL FILTERS
AC Coupling: For applications where only dynamic
accelerations (vibration) are to be measured, it is recommended
to ac couple the accelerometer output as shown in Figure 3.
The advantage of ac coupling is that variations from part to
part of zero g offset and zero g offset versus temperature can
be eliminated. Figure 3 is a HPF (high pass filter) with a –3dB
POWER SUPPLY NOISE REJECTION
Two capacitors and a resistor are recommended for best
rejection of power supply noise (reference Figure 5 below).
The capacitors should be located as close as possible to the
device supply pins (VDA, VDD). The capacitor lead length
should be as short as possible, and surface mount capacitors are
preferred. For typical applications, capacitors C1 and C2 can
be ceramic 0.1 µF, and the resistor R can be 10 Ω.
1
breakpoint given by the equation: f =
. In many
2πRC
applications it may be desirable to have the HPF –3dB point at
a very low frequency in order to detect very low frequency
accelerations. Sometimes the implementation of this HPF may
result in unreasonably large capacitors, and the designer must
turn to digital implementations of HPFs where very low
frequency –3dB breakpoints can be achieved.
V SUPPLY
C1
R
C2
C
VDA
VDD
AOUTX
Filtered
Output
AOUTX
MEMSIC
Accelerometer
R
R
Figure 5: Power Supply Noise Rejection
C
PCB LAYOUT AND FABRICATION SUGGESTIONS
1. The Sck pin should be grounded to minimize noise.
2. Liberal use of ceramic bypass capacitors is recommended.
3. Robust low inductance ground wiring should be used.
4. Care should be taken to ensure there is “thermal
symmetry” on the PCB immediately surrounding the
MEMSIC device and that there is no significant heat
source nearby.
AOUTY
AOUTY
Filtered
Output
Figure 3: High Pass Filter
5. A metal ground plane should be added directly beneath the
MEMSIC device. The size of the plane should be similar
to the MEMSIC device’s footprint and be as thick as
possible.
Low Pass Filter: An external low pass filter is useful in low
frequency applications such as tilt or inclination. The low pass
filter limits the noise floor and improves the resolution of the
accelerometer. The low pass filter shown in Figure 4 has a –
6. Vias can be added symmetrically around the ground plane.
Vias increase thermal isolation of the device from the rest
of the PCB.
1
3dB breakpoint given by the equation: f =
. For the
2πRC
200 Hz absolute output device filter, C=0.2µF and R=39kΩ,
±5%, 1/8W.
R
R
AOUTX
Filtered
Output
AOUTX
C
C
AOUTY
Filtered
Output
AOUTY
Figure 4: Low Pass Filter
MEMSIC MXA2500G/M Rev. E
Page 7 of 8
1/19/2005
LCC-8 PACKAGE DRAWING
Fig 6: Hermetically Sealed Package Outline
MEMSIC MXA2500G/M Rev. E
Page 8 of 8
1/19/2005
相关型号：
MXA6500EP
Low Profile, Low Consumption 0.5 g Dual Axis Accelerometer with Absolute Analog Outputs
ETC
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