ETC1 MXR6999M Low profile, low power â±1.0g dual axis accelerometer with ratiometric output Datasheet

Low Profile, Low Power
±1.0g Dual Axis Accelerometer with
Ratiometric Outputs
MXR6999G/M
FEATURES
Low power consumption: typically 2.0mA @ 3.0V
Resolution better than 1 milli-g
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
Compensated for Sensitivity over temperature
No adjustment needed outside
VDD
TEMP
Internal
Oscillator
TP
VREF
TEMP
CLK
PD
No
Connection
CLK
Coarse
Gain Adj.
Heater
Control
Fine Gain
Adj.
Temp
Comp.
X aixs
APPLICATIONS
CLKTEMP
D/A
CLK
Low Pass Buf.
Filter
CLK
No
Connection
Vref
A/D
CLK
D/A
CLK
Xout
Low Pass Buf.
Filter
Yout
CLK
GND
MXR6999G/M FUNCTIONAL BLOCK DIAGRAM
GENERAL DESCRIPTION
The MXR6999G/M is a 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 MXR6999G/M
measures acceleration with a full-scale range of ±0.6 g and
a sensitivity of 1000mV/g @3V at 25°C. It can measure
both dynamic acceleration (e.g., vibration) and static
acceleration (e.g., gravity). The MXR6999G/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.
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 MXR6999G/M Rev.C
Temp
Comp.
CLK
A/D
Fine Gain
Adj.
Y aixs
Acceleration
Sensor
Vref
CLK TEMP CLK
CLK
Coarse
Gain Adj.
Automotive – Vehicle Security/Active Suspension/ABS
Headlight Angle Control/Tilt Sensing
Security – Gas Line/Elevator/Fatigue Sensing
Office Equipment – Computer Peripherals/PDA’s/Mouse
Smart Pens/Cell Phones
Gaming – Joystick/RF Interface/Menu Selection/Tilt Sensing
White Goods – Spin/Vibration Control
Temperature
Sensor
Page 1 of 6
The MXR6999G/M provides two ratiometric analog
outputs. The maximum noise floor is 1 mg/ Hz
allowing signals below 1 milli-g to be resolved at 1 Hz
bandwidth. The MXR6999G/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.
©MEMSIC, Inc.
800 Turn pike Street, Suite 202, North Andover, MA 01845
Tel: 978.738.0900
Fax: 978.738.0196
www.memsic.com
4/15/2005
MXR6999G/M SPECIFICATIONS (Measurements @ 25°C, Acceleration = 0 g unless otherwise noted; VDD= 3.0V
unless otherwise specified)
MXR6999G
Parameter
Conditions
SENSOR INPUT
Measurement Range1
Nonlinearity
Alignment Error2
Transverse Sensitivity3
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
Each Axis
MXR6999M
Min
Typ
Max
±0.94
±1.0
0.5
±1.0
±2.0
1.0
Best fit straight line
Min
Typ
Max
±0.94
±1.0
0.5
±1.0
±2.0
1.0
Units
g
% of FS
degrees
%
Each Axis
∆ from 25°C
950
-15
1000
1050
+8
950
-20
1000
1050
+8
mV/g
%
-0.1
1.40
0.00
1.50
1.5
1.5
+0.1
1.60
-0.1
1.40
0.00
1.50
1.5
1.5
+0.1
1.60
g
V
mg/°C
mV/°C
0.4
1.0
0.4
1.0
mg/ Hz
17
19
17
19
Each Axis
∆ from 25°C
∆ from 25°C
NOISE PERFORMANCE
Noise Density, rms
FREQUENCY RESPONSE
3dB Bandwidth
SELF TEST
Continuous Voltage at output @3.0V 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
Turn-On Time4
@3V Supply
POWER SUPPLY
Operating Voltage Range
Supply Current
@ 3.0V
TEMPERATURE RANGE
Operating Range
NOTES
15
15
3.0
3.0
2.8
0.2
100
75
2.7
0
V
2.8
0.2
100
3.0
2.0
75
3.6
2.7
+70
-40
3.0
2.0
Hz
V
V
µA
mS
3.6
V
mA
+85
°C
1
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
MEMSIC MXR6999G/M Rev.C
Page 2 of 6
4/15/2005
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (VDD)
………………...-0.5 to +7.0V
Storage Temperature ……….…………-65°C to +150°C
Acceleration ……………………………………..50,000 g
away from the +X direction following the right-hand rule. Small
circle indicates pin one(1).
*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:
Pin
Name
1
PD
2
TP
3
COM
4
NC
5
NC
6
Yout
7
Xout
8
VDD
LCC-8 Package
Description
Power down pin
Connected to ground
Common
Do Not Connect
Do Not Connect
Y Channel Analog Output
X Channel Analog Output
2.7V to 3.6 V
Ordering Guide
Model
Package Type
MXR6999GP
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.
Temperature
Range
LCC8,
RoHS compliant
0 to +70°C
MXR6999MP
LCC8
RoHS compliant
-40 to +85°C
MXR6999GB
LCC8, Pb-free
0 to +70°C
MXR6999MB
LCC8, Pb-free
-40 to +85°C
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.
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°
MEMSIC MXR6999G/M Rev.C
Page 3 of 6
4/15/2005
MEMSIC
PIN DESCRIPTIONS
VDD – 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.
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 ratiometric 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.
X-Axis
X-Axis
Orientation
To Earth’s
Surface
(deg.)
Yout – This pin is the ratiometric output of the Y-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 x-axis, the accelerometer can be programmed for
non-equal sensitivities on the x- and y-axes. Contact the
factory for additional information.
90
85
80
70
60
45
30
20
10
5
0
X Output
(g)
Change
per deg.
of tilt
(mg)
Y-Axis
Y Output
(g)
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
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
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.
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.
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)
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 MXR6999G/M Rev.C
Page 4 of 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
(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.
4/15/2005
PCB LAYOUT AND FABRICATION SUGGESTIONS
1.
2.
3.
4.
Power supply noise rejection
MEMSIC MXR6999G/M Rev.C
5.
Page 5 of 6
It is best to connect a 0.1uF capacitor directly across
VDD 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.
4/15/2005
LCC-8 LOW PROFILE PACKAGE DRAWING
Hermetically Sealed Package Outline
MEMSIC MXR6999G/M Rev.C
Page 6 of 6
4/15/2005
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