Low Profile, Low Power
±1.7g Dual Axis Accelerometer with
Ratiometric Outputs
MXR6500G/M
FEATURES
Low power consumption: typically 2.0mA @ 3.0V
RoHS compliant
Resolution better than 1 mg
Dual axis accelerometer fabricated on a monolithic
CMOS IC
On chip mixed signal processing
No moving parts; No loose particle issues
>50,000
g
shock survival rating
Low profile LCC package: 5mm
X
5mm
X
1.55mm
2.7V to 3.6V single supply continuous operation
No adjustment needed outside
TEMP
TP
Internal
Oscillator
VREF
Temperature
Sensor
TEMP
CLK
PD
CLK
Heater
Control
Coarse
Gain Adj.
Fine Gain
Adj.
No
Connection
Vref
Low Pass
Buf.
Filter
CLK
No
Connection
VDD
X aixs
CLK
Coarse
Gain Adj.
Temp
Comp.
A/D
D/A
CLK
Vref
Xout
CLK TEMP CLK
Fine Gain
Adj.
Temp
Comp.
APPLICATIONS
Automotive –
Vehicle Security/Active Suspension/ABS
Headlight Angle Control/Tilt Sensing
Security
– Gas Line/Elevator/Fatigue Sensing
Office Equipment
– Computer Peripherals/PDA’s/Cell Phones
Gaming
– Joystick/RF Interface/Menu Selection/Tilt Sensing
White Goods
– Spin/Vibration Control
Y aixs
Acceleration
Sensor
CLK
A/D
CLK
D/A
CLK
Low Pass Buf.
Filter
CLK
Yout
CLKTEMP
GND
MXR6500G/M FUNCTIONAL BLOCK DIAGRAM
GENERAL DESCRIPTION
The MXR6500G/M is an low noise and low profile, dual
axis accelerometer fabricated on a standard, submicron
CMOS process. It is a complete sensing system with
on-chip mixed mode signal processing. The MXR6500G/M
measures acceleration with a full-scale range of
±1.7
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 MXR6500G/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 up to
50,000
g,
leading to significantly lower failure rates and
lower loss due to handling during assembly.
The MXR6500G/M provides two ratiometric analog
outputs.
The maximum noise floor is 1 mg/
Hz
allowing signals
below 1mg to be resolved at 1 Hz bandwidth. The
MXR6500G/M is available in a hermetically sealed low
profile LCC surface mount package (5mm x 5mm x
1.55mm).
It is operational over a -40°C to 85°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 Turn pike Street, Suite 202, North Andover, MA01845, USA
Tel: +1 978 738 0900
Fax: +1 978 738 0196
www.memsic.com
MEMSIC MXR6500G/M Rev.C
Page 1 of 6
2/26/2007
MXR6500G/M SPECIFICATIONS
(Measurements
@ 25°C, Acceleration = 0
g
unless otherwise noted; V
DD
= 3.0V
unless otherwise specified)
MXR6500G
Parameter
SENSOR INPUT
Measurement Range
1
Nonlinearity
Alignment Error
2
Transverse Sensitivity
3
SENSITIVITY
Sensitivity, Analog Outputs at
output pins
Change over Temperature
(compensated)
ZERO
g
BIAS LEVEL
0
g
Offset
0
g
Voltage
0
g
Offset over Temperature
Conditions
Each Axis
±1.7
Best fit straight line
0.5
±1.0
±2.0
1.0
±1.7
0.5
±1.0
±2.0
1.0
g
% of FS
degrees
%
Min
Typ
Max
Min
MXR6500M
Typ
Max
Units
Each Axis
∆
from 25°C
Each Axis
-0.1
1.45
∆
from 25°C
∆
from 25°C
0.00
1.50
1.5
0.75
0.4
15
17
+0.1
1.55
-0.1
1.45
0.00
1.50
1.5
0.75
0.4
15
17
+0.1
1.55
g
V
mg/°C
mV/°C
mg/
Hz
Hz
475
500
525
15
475
500
525
20
mV/g
%
NOISE PERFORMANCE
Noise Density, rms
FREQUENCY RESPONSE
3dB Bandwidth
SELF TEST
Continuous Voltage at outputs @3V Supply, output rails to
under failure
supply voltage
OUTPUTS PERFORMANCE
Normal Output Range
Output High
Output Low
Current
Source or sink, @ 2.7V-3.6V
supply
4
Turn-On Time
@3V Supply
POWER SUPPLY
Operating Voltage Range
Supply Current
@ 3V
TEMPERATURE RANGE
Operating Range
NOTES
Guaranteed by measurement of initial offset and sensitivity.
Alignment error is specified as the angle between the true and indicated
axis of sensitivity.
3
Transverse sensitivity is the algebraic sum of the alignment and the
inherent sensitivity errors.
4
Output settled to within
±17mg
.
2
1
1.0
19
1.0
19
3.0
2.8
0.2
100
75
2.7
3.0
2.0
3.6
2.7
2.8
3.0
V
V
V
µA
mS
3.6
V
mA
°C
0.2
100
75
3.0
2.0
0
+70
-40
+85
MEMSIC MXR6500G/M Rev.C
Page 2 of 6
2/26/2007
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (V
DD
)
………………...-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.
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).
Pin Description: LCC-8 Package
Pin
Name
Description
1
PD
Power Down Control
2
TP
Connect to ground
3
COM
Common
4
NC
Do Not Connect
5
NC
Do Not Connect
6
Yout
Y Channel Output
7
Xout
X Channel Output
8
V
DD
2.7V to 3.6V
Ordering Guide
Model
MXR6500GP
MXR6500MP
MXR6500GB
MXR6500MB
I/O
I
I
I
NC
NC
O
O
I
Package Type
LCC8
RoHS compliant
LCC8
RoHS compliant
LCC8, Pb-free
RoHS compliant
LCC8, Pb-free
RoHS compliant
Temperature
Range
0 to +70°C
-40 to +85°C
0 to +70°C
-40 to +85°C
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 except it is a gas in the MEMSIC
sensor.
A single heat source, centered in the silicon chip is
suspended across a cavity. Equally spaced
aluminum/polysilicon thermopiles (groups of
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.
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.
All parts are shipped in tape and reel packaging.
Caution:
ESD (electrostatic discharge) sensitive device.
MEMSIC MXR6500G/M Rev.C
Page 3 of 6
2/26/2007
COM–
This is the ground pin for the
accelerometer
.
TP–
This pin should be connected to ground.
Accelerometer Position Relative to Gravity
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 typical.
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.
Yout
–
This pin is the output of the Y-axis acceleration
MEMSIC
PIN DESCRIPTIONS
V
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.
X-Axis
X-Axis
Orientation
To Earth’s
Surface
(deg.)
90
85
80
70
60
45
30
20
10
5
0
Y-Axis
Change
per deg.
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
X Output
(g)
Change
per deg.
of tilt
(mg)
Y Output
(g)
sensor. The user should ensure the load impedance is
sufficiently high as to not source/sink >100µA typical.
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.
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.
1.000
0.15
0.000
0.996
1.37
0.087
0.985
2.88
0.174
0.940
5.86
0.342
0.866
8.59
0.500
0.707
12.23
0.707
0.500
15.04
0.866
0.342
16.35
0.940
0.174
17.16
0.985
0.087
17.37
0.996
0.000
17.45
1.000
Changes in Tilt for X- and Y-Axes
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.
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.
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 sensing to be
achieved with the MEMSIC device (reference application
note AN-00MX-007).
MEMSIC MXR6500G/M Rev.C
Page 4 of 6
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:
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%).
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
(V
DD
). 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.
2/26/2007
PCB LAYOUT AND FABRICATION SUGGESTIONS
1.
2.
3.
It is best to connect a 0.1uF capacitor directly across
V
DD
and COM pin.
Robust low inductance ground wiring should be used.
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.
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.
Vias can be added symmetrically around the ground
plane. Vias increase thermal isolation of the device
from the rest of the PCB.
4.
5.
Power supply noise rejection
MEMSIC MXR6500G/M Rev.C
Page 5 of 6
2/26/2007
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