mxd2020e memsic, mxd2020e Datasheet - Page 4

• Manufacturer Part Number: mxd2020e
• Description: Ultra Low Noise, Low Offset Drift ?1 G Dual Axis Accelerometer With Digital Outputs
• Manufacturer: memsic

PIN DESCRIPTIONS
V
the sensor heater in the
should be between 3.00 and 5.25 volts. Refer to the section
on PCB layout and fabrication suggestions for guidance on
external parts and connections recommended.
V
amplifiers in the
layout and fabrication suggestions for guidance on external
parts and connections recommended.
Gnd – This is the ground pin for the
D
acceleration sensor. It is factory programmable to 100 Hz
or 400 Hz. 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
sensitivities on the x- and y-axes. Contact the factory for
additional information.
D
acceleration sensor. It is factory programmable to 100 Hz
or 400 Hz. 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
sensitivities on the x- and y-axes. Contact the factory for
additional information.
T
sensor. The analog voltage at T
die temperature. This voltage is useful as a differential
measurement of temperature from ambient and not as an
absolute measurement of temperature. After correlating the
voltage at TOUT to 25°C ambient, the change in this
voltage due to changes in the ambient temperature can be
used to compensate for the change over temperature of the
accelerometer offset and sensitivity. Please refer to the
section on Compensation for the Change in Sensitivity
Over Temperature for more information.
Sck – The standard product is delivered with an internal
clock option (800kHz). This pin should be grounded
when operating with the internal clock. An external
clock option can be special ordered from the factory
allowing the user to input a clock signal between 400kHz
And 1.6MHz
V
at 2.50V typical and has 100μA of drive capability.
MEMSIC MXD2020E/F Rev H
OUTY
OUT
DD
DA
OUTX
ref
accelerometer
accelerometer
– This pin is the output of a reference voltage. It is set
– This is the supply input for the digital circuits and
– This is the power supply input for the analog
– This pin is the buffered output of the temperature
–
– This pin is the digital output of the x-axis
This pin is the digital output of the y-axis
accelerometer
can be programmed for non-equal
can be programmed for non-equal
accelerometer
. Refer to the section on PCB
OUT
is an indication of the
. The DC voltage
accelerometer
.
Page 4 of 8
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. 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 Figure 1 in °C):
where S
S
the temperature values in K.
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. The 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 –0.9%/°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
reference design information on circuits and programs
including look up tables for easily incorporating sensitivity
compensation.
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
f
is the sensitivity at any other final temperature T
i
S
is the sensitivity at any initial temperature T
Figure 1: Thermal Accelerometer Sensitivity
i
2.5
2.0
1.5
1.0
0.5
0.0
x T
-40
i
2.90
-20
= S
f
x T
0
f
Temperature (C)
2.90
20
www.memsic.com
40
60
80
2/26/2007
for
100
f
with
i
, and