Ultra High Performance
±1.5
g
Dual Axis Accelerometer with
I
2
C Interface
MXC6235xQ
FEATURES
RoHS compliant
VDD
TEMP
Internal
Oscillator
VREF
Temperature
Sensor
TEMP
Coarse
Gain Adj.
Fine Gain
Adj.
No
Connect
X aixs
CLK
Coarse
Gain Adj.
Temp
Comp.
A/D
No
Connect
I
2
C Slave, FAST (≤400 KHz) mode interface
1.8V compatible I/O
Ultra Low Noise and initial offset
Embedded Power up/down function
On-chip temperature sensor available
Eight, customer defined 7-bit addresses
2.7 V to 3.6 V single supply continuous operation
Monolithic CMOS IC
Low power consumption: typically <2 mA @ 3.0 V
Resolution better than 1 mg
On chip mixed signal processing
>50,000
g
shock survival rating
Low profile LCC package: 5mm
X
5mm
X
1.55mm
CLK
COM
CLK
Heater
Control
CLK TEMP CLK
Fine Gain
Adj.
Temp
Comp.
IIC Convertor
SCL
SDA
A/D
CLK
CLK
Y aixs
Acceleration
Sensor
CLK
CLKTEMP
GND
APPLICATIONS
Security
– Gas Line, Elevator, Fatigue Sensing
Gaming
– Joystick, RF Interface, Menu Selection,
Tilt Sensing
GPS
–
Electronic Compass Tilt Correction, Dead Reckoning
Consumer –
LCD Projectors, Pedometers, Blood Pressure
Monitor, Digital Cameras
MXC6235xQ FUNCTIONAL BLOCK DIAGRAM
I
nformation Appliances
– Computer Peripherals, PDA’s,
Mouse Smart Pens, Cell Phones
GENERAL DESCRIPTION
The MXC6235xQ 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 MXC6235xQ measures acceleration with
a full-scale range of
±1.5
g
and a sensitivity of 512counts/g
at @3.0 V at 25
°C
. It can measure both dynamic
acceleration (e.g. vibration) and static acceleration (e.g.
gravity). The MXC6235xQ design is based on heat
convection and requires no solid proof mass.
This design eliminates the stiction problems associated with
legacy technologies and provides shock survival greater
than 50,000g’s.
Information furnished by MEMSIC is believed to be accurate and reliable. However,
no responsibility is assumed by MEMSIC for its use, or 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’s solid state design leads to significantly lower
failure rates in customer applications and lower loss due to
handling during manufacturing and assembly processes
The MXC6235xQ provides I
2
C digital output with 400
KHz. fast mode operation.
The typical noise floor is 0.13 mg/
Hz
allowing signals
below 0.5m
g
to be resolved at 1 Hz bandwidth.
The MXC6235xQ is packaged in a hermetically sealed, low
profile LCC surface mount package (5 mm x 5 mm x 1.55
mm) and is available in operating temperature ranges of -
40°C to +105°C (MXC6235xQB) or -20°C to +105°C
(MXC6235xQP)
©MEMSIC,
Inc.
One Technology Drive, Suite 325, Andover, MA01810, USA
Tel: +1 978 738 0900
Fax: +1 978 738 0196
www.memsic.com
MEMSIC MXC6235xQ Rev.C
Page 1 of 9
11/30/2010
otherwise specified)
ELECTRICAL CHARACTERISTICS
(Measurements @ 25°C, Acceleration = 0
g
unless otherwise noted; V
DD
= 3.0V unless
Parameter
Measurement Range
1
Nonlinearity
Alignment Error
2
Transverse Sensitivity
3
Sensitivity
Sensitivity Change Over Temperature
Conditions
Each Axis
Best fit straight line
Min
±1.5
Typ
0.5
±1.0
±2.0
512
Max
1.0
Units
G
% of FS
degrees
%
counts/g
%
486
Δ
from 25°C at -20°C
Δ
from 25°C at -40°C
Δ
from 25°C at 105°C
Δ
from 25°C
3195
0.18
@ 1Hz. BW
@ -3dB
@ 2.7 V – 3.6 V
-60
-0.05
2022
538
+80
+160
+0.05
2074
0.5
3555
0.26
0.5
10
100
200
3.6
1.0
+105
+105
Zero
g
Offset Bias Level
Zero
g
Offset TC
Tout
Tout Sensitivity
Noise Density, RMS
Resolution
Frequency Response
Output Drive Capability
Turn-On Time
4
Operating Voltage Range
Supply Current
Power Down Current
Operating Temperature Range
NOTES:
1
2
0.0
2048
0.1
3375
0.22
0.15
0.2
8
150
3.0
1.8
g
counts
m
g
/°C
counts
°C/count
m
g
/
Hz
mg
Hz
μA
mS
V
mA
μA
°C
°C
6
2.7
MXC6235xQB
MXC6235xQP
-40
-20
Guaranteed by measurement of initial offset and sensitivity
Alignment error is specified as the angle between the true and indicated
axis of sensitivity
Cross axis sensitivity is the algebraic sum of the alignment and the
inherent sensitivity errors
Output settled to within
±
17mg
3
4
MEMSIC MXC6235xQ
Rev.C
Page 2 of 9
11/30/2010
I
2
C INTERFACE I/O CHARACTERISTICS
Parameter
Logic Input Low Level
Logic Input High Level
Hysteresis of Schmitt input
Logic Output Low Level
Input Leakage Current
SCL Clock Frequency
START Hold Time
START Setup Time
LOW period of SCL
HIGH period of SCL
Data Hold Time
Data Setup Time
Rise Time
Fall Time
Bus Free Time Between STOP and
START
STOP Setup Time
Symbol
V
IL
V
IH
V
hys
V
OL
I
i
f
SCL
t
HD;STA
t
SU;STA
t
LOW
t
HIGH
t
HD;DAT
t
SU;DAT
t
r
t
f
t
BUF
t
SU;STO
Test Condition
Min.
-0.5
0.7*V
DD2
0.2
Typ.
Max.
0.3*V
DD2
V
DD2
0.4
Unit
V
V
V
0.1V
DD2
<V
in
<0.9
V
DD2
-10
0
0.6
0.6
1.3
0.6
0
0.1
10
400
µA
kHz
µS
µS
µS
µS
0.7* t
LOW
0.3
0.3
µS
µS
µS
µS
µS
µS
From V
IL
to V
IH
From V
IH
to V
IL
1.3
0.6
SDA
t
f
t
LOW
t
r
t
SU;DAT
t
f
t
HD;STA
t
SP
t
r
t
BUF
SCL
t
HD;STA
t
HIGH
t
SU;STA
Sr
t
SU;STO
P
S
S
t
HD;DAT
Timing Definition
MEMSIC MXC6235xQ
Rev.C
Page 3 of 9
11/30/2010
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (V
DD
) ………………...-0.5 V to +7.0V
Storage Temperature
（MXC6235xQB）-65°C
to +150°C
Storage Temperature
（MXC6235xQP）-30°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
Name
Description
1
NC
Do Not Connect
2
COM
Connected to Ground
3
GND
Connected to Ground
4
TEST
Do Not Connect
5
VDD2 Power Supply for I
2
C bus
6
SCL
Serial Clock Line for I
2
C bus
7
SDA
Serial Data Line for I
2
C bus
8
V
DD
2.7 V to 3.6 V
Ordering Guide
MXC6235xQB
I/O
NC
I
I
NC
I
I
I/O
I
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).
Package type and temperature range:
Code
Type
B
LCC8, Pb-free
RoHS compliant
-40°C~105°C
P
LCC8,
RoHS compliant
-20°C~105°C
Performance Grade:
Code
Resolution
Q
4096counts
MXC6235xQB
Address code: 0~7
Number Address
0
20H
1
22H
2
24H
3
26H
4
28H
5
2AH
6
2CH
7
2EH
All parts are shipped in tape and reel packaging.
Caution:
ESD (electrostatic discharge) sensitive device.
MXC6235xQP
MEMSIC MXC6235xQ
Rev.C
Page 4 of 9
11/30/2010
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
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.
MXC6235Q 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.
GND–
This is the ground pin for the
accelerometer
.
COM–
This pin should be connected to ground.
TEST–
Do Not Connect, factory use only.
VDD2–
This pin is the I
2
C input digital power supply, the
voltage on this pin determines the I
2
C bus logic voltage,
and is 1.8V compatible. Note: The voltage on this pin
should never go higher than the voltage on V
DD
, if VDD2
has a lower power supply voltage than V
DD
, power should
be applied to V
DD
first.
SDA–
This pin is the I
2
C serial data line, and operates in
FAST (400 KHz.) mode.
SCL–
This pin is the I
2
C serial clock line, and operates in
FAST (400 KHz.) mode.
COMPENSATION FOR 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. The sensitivity change is governed by the
following equation (and shown in following figure in
°C):
S
i
x T
i2.9
= S
f
x T
f2.9
where S
i
is the sensitivity at any initial temperature T
i
, and
S
f
is the sensitivity at any other final temperature T
f
with
the temperature values in
°K.
2.5
Sensitivity (normalized)
2.0
1.5
1.0
0.5
0.0
-40
-20
0
20
40
60
80
100
Temperature (C)
Thermal Accelerometer Sensitivity
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.
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 +105°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.
MEMSIC MXC6235xQ
Rev.C
Page 5 of 9
11/30/2010
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