MXA6500EP [ETC]
Low Profile, Low Consumption 0.5 g Dual Axis Accelerometer with Absolute Analog Outputs; 薄型，低功耗0.5克双轴加速度计具有绝对模拟输出
| 型号： | MXA6500EP |
| 厂家： | 
ETC |
| 描述： | Low Profile, Low Consumption 0.5 g Dual Axis Accelerometer with Absolute Analog Outputs |
| 文件： | 总6页 (文件大小：88K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Low Profile, Low Consumption
±0.5 g Dual Axis Accelerometer with
Absolute Analog Outputs
MXA6500E
VDD
FEATURES
TEMP
Low power consumption: typical 2mA@3V
Resolution better than 1 milli-g
Dual axis accelerometer fabricated on a monolithic
CMOS IC
On chip mixed signal processing
No moving parts
Temperature
Internal
VREF
Sensor
TP
PD
Oscillator
TEMP
No
Connection
CLK
CLK
Coarse
Fine Gain
Adj.
Heater
Control
Gain Adj.
Vref
D/A
No loose particle issues
Low Pass
Filter
Temp
Xout
A/D
Buf.
Buf.
>50,000 g shock survival rating
5mm X 5mm X 1.55mm LCC package
2.7V to 3.6V single supply continuous operation
Ultra low initial Zero-g Offset
No adjustment needed outside
X aixs
Comp.
CLK TEMP
CLK
CLK
CLK
CLK
Vref
No
Connection
Coarse
Fine Gain
Adj.
Gain Adj.
Temp
Low Pass
Filter
Y aixs
Yout
A/D
D/A
Comp.
Acceleration
Sensor
CLK
CLK
CLK
TEMP
CLK
CLK
APPLICATIONS
GND
Tilt and motion sensing in cost-sensitive applications
Smart handheld devices
Computer security
Input devices
MXA6500E FUNCTIONAL BLOCK DIAGRAM
Pedometers and activity monitors
Gaming controllers
Toys and entertainment products
GENERAL DESCRIPTION
The MXA6500E is a low cost; dual axis accelerometer
fabricated on a standard, submicron CMOS process. It is a
complete sensing system with on-chip mixed signal
processing. The MXA6500E measures acceleration with a
full-scale range of ±0.5 g and a sensitivity of 500mV/g @3V
at 25°C. It can measure both dynamic acceleration (e.g.
vibration) and static acceleration (e.g. gravity). The
MXA6500E 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 greater than 50,000 g, leading to significantly
lower failure rate and lower loss due to handling during
assembly and at customer field application.
The max noise floor is 1 mg/ Hz allowing signals below
1 milli-g to be resolved at 1 Hz bandwidth. The
MXA6500E is packaged in a hermetically sealed lowprofile
LCC surface mount package (5 mm x 5 mm x 1.55 mm
height). It is operational over a -40°C to +85°C 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 MXA6500E Rev.B
Page 1 of 6
3/22/2005
MXA6500E SPECIFICATIONS (Measurements @ 25°C, Acceleration = 0 g unless otherwise noted; VDD = 3.0V unless otherwise
specified)
MXA6500E
Parameter
Conditions
Units
Min
Typ
Max
SENSOR INPUT
Each Axis
Measurement Range1
g
±0.5
Nonlinearity
Best fit straight line
X Sensor to Y Sensor
Each Axis
0.5
±1.0
0.01
±2
1.0
% of FS
degrees
degrees
%
Alignment Error2
Alignment Error
Cross Axis Sensitivity3
SENSITIVITY
Sensitivity,
VDD = 3.0V
475
-50
500
525
155
mV/g
%
Sensitivity Change over
Temperature4
Delta from 25°C at -40°C
Delta from 25°C at +85°C
Each Axis
ZERO g BIAS LEVEL
0 g Offset
VDD = 3.0V
1.20
-0.10
1.25
0.00
0.5
1.30
0.10
V
g
mg/°C
0 g Offset
0 g Offset vs. Temperature4
Delta from 25°C
@25°C
NOISE PERFORMANCE
Noise Density, rms
FREQUENCY RESPONSE
3dB Bandwidth
0.4
17
1.0
19
mg/ Hz
15
Hz
POWER SUPPLY
Operating Voltage Range
Quiescent Supply Current
OUTPUTS PERFORMANCE
Output High Voltage
Output Low Voltage
Current
2.7
3.6
V
mA
@3.0V supply
@3.0V supply
2.0
2.30
-40
V
V
uA
0.20
100
Source or sink @ 3.0V-3.6V Supply
@3.0V supply
Turn-On Time5
TEMPERATURE RANGE
Operating Range
75
mS
+85
°C
NOTES
1
Guaranteed by measurement of initial offset and sensitivity.
2
Alignment error is specified as the angle between the true and indicated axis of
sensitivity.
3
Cross axis sensitivity is the algebraic sum of the alignment and the inherent
sensitivity errors.
4 Defined as the output change from ambient to maximum temperature or ambient to
minimum temperature.
5 Output settled to within ±17mg.
MEMSIC MXA6500E Rev.B
Page 2 of 6
3/22/2005
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (VDD ………………...-0.5 to +7.0V
)
Storage Temperature ……….…………-65°C to +150°C
Acceleration ……………………………………..50,000 g
*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.
Pin Description: LCC-8 Package
Pin
1
2
3
4
5
6
7
8
Name
PD
TP
COM
NC
NC
Yout
Xout
VDD
Description
Power Down Control
Connect to ground
Common
Do Not Connect
Do Not Connect
Y Channel Output
X Channel Output
2.7V to 3.6V
THEORY OF OPERATION
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.
Ordering Guide
Model
Package Style
Temperature Range
LCC8
RoHS compliant
A single heat source, centered in the silicon chip is
suspended across a cavity. Equally spaced
aluminum/polysilicon thermopiles (groups of
MXA6500EP
MXA6500EB
-40 to 85°C
-40 to 85°C
LCC8, Pb-free
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.
All parts are shipped in tape and reel packaging.
Caution: ESD (electrostatic discharge) sensitive device.
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.
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)
MEMSIC MXA6500E Rev.B
Page 3 of 6
3/22/2005
PIN DESCRIPTIONS
DD – This is the supply input for the circuits and the
sensor heater in the accelerometer. The DC voltage should
be between 2.7 and 3.6 volts. Refer to the section on PCB
layout and fabrication suggestions for guidance on external
parts and connections recommended.
2.5
2.0
1.5
1.0
0.5
0.0
V
COM– This is the ground pin for the accelerometer.
TP- This pin should be connected to the ground.
-40
-20
0
20
40
60
80
100
Temperature (C)
Thermal Accelerometer Sensitivity
Xout – 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.
In gaming applications where the game or controller is
typically used in a constant temperature environment,
sensitivity might not need to be compensated in hardware
or software. Any compensation for this effect could be
done instinctively by the game player.
For applications where sensitivity changes of a few percent
are acceptable, the above equation can be approximated
with a linear function. Using a linear approximation, an
external circuit that provides a gain adjustment of –1.1%/°C
would keep the sensitivity within 10% of its room
temperature value over a 0°C to +50°C range.
Yout – 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.
For applications that demand high performance, a low cost
micro-controller can be used to implement the above
equation. A reference design using a Microchip MCU (p/n
16F873/04-SO) and MEMSIC developed firmware is
available by contacting the factory. With this reference
design, the sensitivity variation over the full temperature
range (-40°C to +85°C) can be kept below 3%. Please visit
the MEMSIC web site at www.memsic.com for reference
design information on circuits and programs including look
up tables for easily incorporating sensitivity compensation.
PD – Pin 1 is the power down control pin. Pull this pin HIGH
will put the accelerometer into power down mode. When the part
goes into power down mode, the total current will be smaller than
0.1uA at 3V.
In normal operation mode, this pin should be connected to
Ground.
COMPENSATION FOR THE CHANGE IN
SENSITIVITY OVER TEMPERATURE
DISCUSSION OF TILT APPLICATIONS AND
RESOLUTION
All thermal accelerometers display the same sensitivity
change with temperature. The sensitivity change depends
on variations in heat transfer that are governed by the laws
of physics. The sensitivity change is governed by the
following equation (and shown in following figure in °C):
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.
Si x Ti3.40 = Sf x Tf3.40
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 the force of gravity (perpendicular to the Earth’s
surface), it is least sensitive to changes in tilt.
where Si is the sensitivity at any initial temperature Ti, and
Sf is the sensitivity at any other final temperature Tf with
the temperature values in °K.
Following table and figure 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
MEMSIC MXA6500E Rev.B
Page 4 of 6
3/22/2005
sensing to be achieved with the MEMSIC device (reference
application note AN-00MX-007).
POWER SUPPLY NOISE REJECTION
One capacitor is recommended for best rejection of power
supply noise (reference figure below). The capacitor should
be located as close as possible to the device supply pin
(VDD). The capacitor lead length should be as short as
possible, and surface mount capacitor is preferred. For
typical applications, the capacitor can be ceramic 0.1 µF.
Accelerometer Position Relative to Gravity
X-Axis
Y-Axis
X-Axis
Orientation
Change
Change
To Earth’s
X Output per deg. Y Output per deg.
Surface
(deg.)
90
(g)
of tilt
(mg)
0.15
1.37
2.88
(g)
of tilt
(mg)
17.45
17.37
17.16
16.35
15.04
12.23
8.59
5.86
2.88
1.37
0.15
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
Power Supply Noise Rejection
85
80
70
60
45
30
20
10
5.86
8.59
PCB LAYOUT AND FABRICATION SUGGESTIONS
12.23
15.04
16.35
17.16
17.37
17.45
1. It is best to solder a 0.1uF capacitor directly across VDD
and COM pin.
2. Robust low inductance ground wiring should be used.
3. 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.
5
0
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:
4. 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.
5. Vias can be added symmetrically around the ground
plane. Vias increase thermal isolation of the device
from the rest of the PCB.
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%).
MEMSIC MXA6500E Rev.B
Page 5 of 6
3/22/2005
LCC-8 LOW PROFILE PACKAGE DRAWING
Hermetically Sealed Package Outline
MEMSIC MXA6500E Rev.B
Page 6 of 6
3/22/2005
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