MXD2020GL datasheet(4/7 Pages) ETC

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MEMSIC MXD2020GL/ML/NL/HL

Page 4 of 7

2002.08.29.1

MXD2020GL/HL/ML/NL PIN DESCRIPTIONS

VDD – This is the supply input for the digital circuits and

the sensor heater in the accelerometer. The DC voltage

should be between 3.0 and 5.25 volts. Refer to the section

on PCB layout and fabrication suggestions for guidance on

external parts and connections recommended.

VDA – This is the power supply input for the analog

amplifiers in the accelerometer. VDA should always be

connected to VDD. 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.

DOUTX – This pin is the digital output of the x-axis

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 >100

µA 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.

DOUTY – This pin is the digital output of the y-axis

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 >100

µA 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.

TOUT – This pin is the buffered output of the temperature

sensor. The analog voltage at TOUT is an indication of the

die temperature. This voltage is useful as a differential

measurement of temperature from ambient and not as an

absolute measurement of temperature.

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

Vref – A reference voltage is available from this pin. It is

set at 2.50V typical and has 100

µA of drive capability.

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.

Table 1 and Figure 2 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).

Top View

+900

gravity

Figure 2: Accelerometer Position Relative to Gravity

X-Axis

Y-Axis

X-Axis

Orientatio

To Earth’s

Surface

(deg.)

X Output

(g)

Change

per deg.

of tilt

(mg)

Y Output

(g)

Change

per deg.

of tilt

(mg)

1.000

0.15

0.000

17.45

0.996

1.37

0.087

17.37

0.985

2.88

0.174

17.16

0.940

5.86

0.342

16.35

0.866

8.59

0.500

15.04

0.707

12.23