MXR7250VW Datasheet by Memsic Inc.

MXR7250VW
MEMSIC MXR7250VW Rev.C Page 1 of 6 6/06/2008
Low Cost ±5 g Dual-Axis Accelerometer
with Ratiometric Outputs
MXR7250VW
FEATURES
Dual axis accelerometer fabricated on a single CMOS IC
Monolithic design with mixed mode signal processing
RoHS compliant
On-chip sensitivity compensation for temperature variations
On Demand Self Test
± 5g dynamic range, 250mV/g sensitivity
Independent axis programmability (special order)
Resolution better than 1mg
Zero-g Output Temperature drift, better than ±80mg over
–40~95degC range
27Hz bandwidth
>50,000 g shock survival rating
4.50V to 5.25V single supply operation
Small surface mount package, 5.5mm x 5.5mm x 2.7mm
APPLICATION
Automotive – Roll over sensing, VSC/EPB application
VDD
Vref
CLK
TP
No
CLK CLKTEMP
TEMP
CLK CLK TEMP CLK CLK
Temp
Comp.
Temp
Comp.
X axis
Y axis
CLK
Heater
Control
TEMP
No
Connection
No
Connection
Xout
Yout
Low Pass
A/D
Temperature
Sensor
Internal
Oscillator
Coarse
Gain Adj. Fine Gain
Adj.
GND
Acceleration
Sensor
Coarse
Gain Adj. Fine Gain
Adj.
Connection
CLK
D/A Filter
Vref
Buf.
CLK CLK
Low Pass
A/D
CLK
D/A Filter
Vref
Buf.
MXR7250VW FUNCTIONAL BLOCK DIAGRAM
GENERAL DESCRIPTION
The MXR7250VW is a low cost, dual axis accelerometer
built on a standard, submicron CMOS process. It measures
acceleration with a full-scale range of ±5g and a sensitivity
of 250mV/g.
The MXR7250VW provides a g-proportional ratiometric
analog output above/below the zero-g point at 50% of the
supply voltage.
(Ref. other MEMSIC data sheets for absolute analog or
digital outputs).
The typical noise floor is 0.6mg / Hz , allowing signals
below 1mg to be resolved at 1Hz bandwidth. The 3dB roll-
off of the device occurs at 27Hz.
The MXR7250VW is packaged in a hermetically sealed
LCC surface mount package (5.5 mm x 5.5 mm x 2.7 mm
height), and the package can be used as both XY and XZ
sensing, its operation temperature is -40°C to +95°C.
Memsic’s accelerometer technology allows for designs
from ±1 g to ±70 g with custom versions available above
±70 g. It can measure both dynamic acceleration (e.g.,
vibration) and static acceleration (e.g., gravity).
The design is based on heat convection and requires no
solid proof mass. This eliminates stiction and particle
problems associated with competitive devices and provide
shock survival greater than 50,000 g, leading to
significantly lower failure rates and lower loss due to
handling during assembly and at customer field application.
Due to the standard CMOS structure of the MXR7250VW,
additional circuitry can easily be incorporated into custom
versions for high volume applications. Contact Memsic’s
local office for more information.
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.
One Technology Drive, Suite 325, Andover, MA01810, USA
Tel: +1 978 738 0900 Fax: +1 978 738 0196
www.memsic.com
257 2S7 A‘C~9S’ A‘C~9S’ O7C~95°
MEMSIC MXR7250VW Rev.C Page 2 of 6 6/06/2008
MXR7250VW SPECIFICATIONS (Measurements @ 25°C, Acceleration = 0 g unless otherwise noted; VDD = 5.0V
unless otherwise specified)
Parameter
Conditions
Min MXR7250V
Typ Max
Units
SENSOR INPUT
Measurement Range1 Each Axis
±5.0
g
No linearity Best fit straight line 0.5 1.0 % of FS
Alignment Error2
±0.2 degrees
Transverse Sensitivity3
±0.5 ±1.0 %
SENSITIVITY
Sensitivity, Analog Outputs at pins
Xout and Yout4
Each Axis
@5.0V supply
235
250
265
mV/g
Sensitivity Ratiometricity 5V+/-5% 1.0 2.0 %
Change over Temperature Δ from 25°C –40°C to +95°C -6 +3 %
ZERO g BIAS LEVEL
0 g Offset Each Axis
-0.20
0.00
+0.20
g
0 g Voltage 2.45 2.50 2.55 V
0 g Offset Ratiometricity 5V+/-5% 1.0 %
0 g Offset over Temperature Δ from 25°C, based on 250mV/g
±80 mg
NOISE PERFORMANCE
Noise Density, rms
–40°C to +95°C
0.6
1.5
mg/ Hz
FREQUENCY RESPONSE
3dB Bandwidth 24 27 30 Hz
Phase delay at 5Hz -18 deg
SELF TEST
at 25°C, 0g input -650 -830 -1000 mV
at 25°C, 1g input -700 -850 -1050 mV
at 25°C, -1g input -600 -900 -1100 mV
-40°C~95°C, 0g input -600 -1100 mV
-40°C~95°C, 1g input -500 -1500 mV
Delta Output changes at Xout, Yout
-40°C~95°C, -1g input -600 -1600 mV
Selftest Input Voltage High
Low 4.0
1.0 V
V
Selftest Response Time 20 25 30 mS
Self Test Pin Pull-Down Resistor (Internal) 50 Kohms
Xout and Yout/Zout OUTPUTS
Normal Output Range
(Guaranteed symmetric clipping)
0.5
4.5
V
Current Source or sink, @ 4.5V-5.25V supply 100 μA
Resistance 100 ohm
Capacitance 100 pF
Turn-On Time @5.0V Supply 80 mS
POWER SUPPLY
Operating Voltage Range 4.5 5.0 5.25 V
Supply Current5 @ 5.0V RMS 3.2 4.1 5.0 mA
TEMPERATURE RANGE
Operating Range -40 +95 °C
PRESSURE RANGE
Operating Range 40 300 KPa.
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 Transverse sensitivity is the algebraic sum of the alignment and the
inherent sensitivity errors.
4 The device operates over a 4.5V to 5.25V supply range. The output zero
g reference voltage scales 50% of the supply voltage. Sensitivity has a
linear scale over the supply range of 4.5 to 5.25 volts according to the ratio
(Vdd/5.0 volts) x (250mV/g).
recommended to filter with a minimum of 200Hz low pass filter.
5 Note that the accelerometer has a constant heater power control circuit
thereby requiring higher supply current at lower operating voltage.
ABSOLUTE MAXIMU Supply Voltage (VDD. vD ESD Culnpliance: Storage Temperature The MXR7ZSOV sensor is in compllallcc w standards, Storage Pressure... Acceleration (any axrs, U ed for 0.5 msec) Acceleration (any axrs, P 0.5 msec) Output Short Cucuu Duran 0 common Human Body and ZSOUV per AEC-QlflO-O Machlllc Model and 250V per AEC-QlOO-O ,Illdcflllitc xv Sensing: strt-rrer rrnt- trtrrt- rrrtn rrera arrtrirre Mrrrrrrr nirrtr rrrr perrrrrert nrrrre re .re tr rrr. r trrer rrt.rt trrir. trt lrrtrtrra per.tr tr rre nt-r .r trt-rt tr, ttrt-r t-trrnrtrrr .rtrre rrrrre .rtntrttn .r trt rrptrrrrra rett.trr tr rrrr rpetn trrr .r rtrt .rrpren Eprrr rtr .rrrtrrre rrrrrrrrr rung rrrrrrrrat ltrr ettrrat-a pt-rrrar rte rnet. tre.te rcllahlhly Pin Description: LCC Package O I Expuxure fm up u» M! minutes to uhwluie minlmum mungx for supply voltages will not nl‘t‘ecr deuce reliability Pin Name Description 1 NC Do Not Connect 2 Xout x Channel Output 3 VW 4.5Vto5.25v I I I 2 I I 3 I I 4 STm Selfiesl 5/1 NC/NC Do Not Connect 6/M CLK/CLK Ground (Tup View, do not scale) 7/L COM/COM Ground X/K YouIJZoul Y Channel OulpuL/Z Note: Small cllclc mdlcalcs plll seven (7), channel output (x2 sensing) xz Sensing: Ordering Guide M L K Model Package Style Temperature Range MXR7250VW LCC p40 to 95°C Roi-ls compliant All parts are shipped in rape and reel packaging l 2 3 Caution: ESD (electrostatic discharge) sen we device —,+x 1 zsv (notion. View, do not sea ME fill—lml’ Ll x=z so TOP new J v=z 7; mm in Scalet 1 MEM§> j ‘I Q'fwew EARl‘H 5 SURFACE MEMSIC MXR7250VW Re\'.C Page 3 off: 6/06/2008
MEMSIC MXR7250VW Rev.C Page 3 of 6 6/06/2008
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (VDD, VDA) ¹ ……………...-0.5 to +7.0V
Storage Temperature ……….…………-70°C to +150°C
Storage Pressure…………………………………1,378 kPa
Acceleration (any axis, Un-powered for 0.5 msec)..50,000 g
Acceleration (any axis, Powered for 0.5 msec)…… .2,000 g
Output Short Circuit Duration, any pin to common…….Indefinite
*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.
¹ Exposure for up to 60 minutes to absolute maximum ratings for supply
voltages will not affect device reliability.
Pin Description: LCC Package
Pin Name Description
1 NC Do Not Connect
2 Xout X Channel Output
3 VDD 4.5V to 5.25V
4 STIN Selftest
5/J NC/NC Do Not Connect
6/M CLK/CLK Ground
7/L COM/COM Ground
8/K Yout/Zout Y Channel Output/Z
channel output (XZ sensing)
Ordering Guide
Model Package Style Temperature
Range
MXR7250VW LCC
RoHS compliant -40 to 95°C
All parts are shipped in tape and reel packaging.
Caution: ESD (electrostatic discharge) sensitive device.
ESD Compliance:
The MXR7250V sensor is in compliance with the following ESD
standards:
Human Body and 2500V per AEC-Q100-002 Rev. E
Machine Model and 250V per AEC-Q100-003 Rev. E
XY Sensing:
(Top View, do not scale)
Note: Small circle indicates pin seven (7).
XZ Sensing:
(Bottom View, do not scale)
X=2.25V
Y=2.50V
X=2.50V
Y=2.75V TOP VIEW
(Not to Scale)
X=2.75V
Y=2.50V
X=2.50V
Y=2.50V
EARTH’S SURFACE
ML K J
1 2 3 4
+X
X=2.50V
Y=2.25V
7
8
6
5
1 2 3 4
+Y
+X
MEMSIC MXR7250VW Rev.C Page 4 of 6 6/06/2008
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 MXR7250VW, one to
measure acceleration in the x-axis and one to measure
acceleration in the Y-axis. For more details visit the
MEMSIC website at www.memsic.com for a
picture/graphic description of the free convection heat
transfer principle.
PIN DESCRIPTIONS
VDD – Supply voltage input for digital and analog circuits.
For proper operation VDD must be between 4.50 and 5.25
volts. Refer to the section on PCB layout and fabrication
suggestions for guidance on external parts and connections
recommended.
Xout – X-axis acceleration signal output
It is capable of sinking or sourcing up to 100μA. 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 MXR7250VW can be
programmed for non-equal sensitivities on the x- and y-
axes.
Contact Memsic’s local office for additional information.
Yout /Zout– Y-axis acceleration signal output.
It is capable of sinking or sourcing up to 100μA. 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 MXR7250VW can be
programmed for non-equal sensitivities on the X- and Y-
axes.
Contact Memsic’s local office for additional information.
NC – No connect. These pins can be tied to common if the
application does not allow pins to remain unconnected.
COM – This is the ground pin for the MXR7250VW
CLK – This is an optional serial clock input. The standard
product is delivered with an internal clock (1000 kHz).
However, an external clock between 400 kHz and 1.6 MHz
can be used as an option, if the sensor is programmed from
the factory to run in external clock mode.
This pin is grounded internally with a 50 Kohm resistor if
an external clock is used it should be able to drive this load.
But if external clock is not used, in order to minimize noise
and ESD this pin should be grounded externally as well.
STIN– Self –Test Input
This pin controls the self-test function of the sensor.
Bringing STIN high will cause a negative deflection around
830mV to the AoutX AoutY from the 0g value.
–
0 10 20 30 40 50 60 70 80 90100110
Time - millisec
Self
Test
AOUT
X
AOUT
Y
Xout
Yout
SELF-TEST DESCRIPTION When Selfrlesl is enabled the sensitivity compensation is turned off (disabled). With the sensitivity compensation disabled. the l.0g offse voltages will double its value as compared with the zero g condition. with an exponent of 2.8 in the equation. the sensitivity will be (298K / 233K)2 K = 2.00 times larger 95v x:totlv 70v y:t7tlv L J“ L :I g I: j % E 2 2 j W W F j W W V7 TOP VIEW TOP VIEW (N01 roScaley (NDHUS ale) 740°C 95°C J L1 Li L J L1 Li L i S :| £7 I: :| E E ‘i ai’ x:l7th ° y:t7tlv j V 4W x:tx0v , 70v L] Li Li Li y:t7tlv H W W W EARTH’S SURFACE The gas law governs the change in sensitivity over [em eralure. All thermal accelerometers display the same sensitivity change with temperature, The sensitivity change depends on variations in heat tran. er that are governed by the laws of phy ics, Manufacturing variations do not influence the sensitivity change. so there are no uniirioelmil differences in sensitivity change. The sensitivity change is governed by the following equation (and shown in the following figure in ”C): SixTizx=kXStXlex where s. is the sensitivity at any initial temperature T,, and St is the sensitivity at any other t‘inal temperature T. With the Iemperalure values in ”C, k is [he ralio between uncompensated sensitivity and compensated sensitivity at 25°C. MEMSIC MXR7250VW Re\'.C Page 5 off: (mm. mi Shrumv on 20 a 20 40 so so too Ylmvllalun to) 77181111“,AL’(BIHV
MEMSIC MXR7250VW Rev.C Page 5 of 6 6/06/2008
SELF-TEST DESCRIPTION
When Self-test is enabled the sensitivity compensation is
turned off (disabled). With the sensitivity compensation
disabled, the 1.0g offset voltages will double it’s value as
compared with the zero g condition. With an exponent of
2.8 in the equation, the sensitivity will be (298K / 233K)2.8
= 2.00 times larger
The gas law governs the change in sensitivity over
temperature.
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. Manufacturing variations do not influence the
sensitivity change, so there are no unit-to-unit differences in
sensitivity change. The sensitivity change is governed by
the following equation (and shown in the following figure
in °C):
S
i x Ti2.8 = k x Sf x Tf2.8
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 °C, k is the ratio between
uncompensated sensitivity and compensated sensitivity at
25°C.
.
0.0
0.5
1.0
1.5
2.0
2.5
-40-200 20406080100
Temperature (C)
Sensitivity (normalized
)
Thermal Accelerometer Sensitivity
.
MEMSIC
Accelerometer Position Relative to Gravity
Note1: When the temperature compensation is disabled and
self-test is enabled. Self-test follows different gas law from
sensitivity temperature dependence. It changes much
smaller than sensitivity; this is why the temperature
compensation is not done on self-test conditions.
Note2: Initial offset monitoring is a much better and
reliable method to ensure sensor integrity, since it is ultra
sensitive to sensor structure defect and damage. As long as
initial offset is within specification the sensor is functioning
correctly.
The sensor structure for the Thermal technology is
guaranteed to fall outside the specified initial zero g offset
parameters if the sensor is damaged or thermopile is failing.
In most cases this will result in the output voltage hitting
the rail at 5.0 volts.
TOP VIEW
(Not to Scale)
-40°C
X=1.80V
Y=1.70V
X=1.70V
Y=1.70V
TOP VIEW
(Not to Scale)
95 °C
X=1.95V
Y=1.70V
X=1.41V
Y=1.70V
X=1.60V
Y=1.70V
EARTH’S SURFACE
I ////i« 47‘ /L/ W// 7 ‘4m Z 7% g ‘ W 7, 4 ” 1 r ’ W/M 7//// /// % ”11/424 M W J ‘ {,h,
MEMSIC MXR7250VW Rev.C Page 6 of 6 6/06/2008
PCB LAYOUT AND FABRICATION SUGGESTIONS
Reference figure and the notes below for recommendations
on connecting a power source to the MEMSIC device and
PCB fabrication.
Notes:
1. C1 = 1.0μF
2. The capacitor should be located as close as possible to
the device supply pin VDD, since the internal heater is
in PWM (1MHz) control mode, with all VDD on the
heater at some portion of the time, by using larger
value capacitor can minimize the induced noise on the
outputs.
3. The CLK is grounded internally with a 50 kOhm
resistor, however, in order to minimize noise and ESD
this pin should be grounded externally as well.
4. Robust low inductance ground wiring should be used.
5. Care should be taken (like isolated rings and planes,
signal route out perpendicular to the external thermal
gradient) to ensure there is “thermal symmetry” on the
PCB immediately surrounding the MEMSIC device
and that there is no significant heat source nearby. This
will minimize any errors in the measurement of
acceleration.
PCB Layout
PACKAGE OUTLINE
Dimensions shown in mm.
CERAMIC
(BLACK)
C1