SCA103T Series

Murata Electronics Oy

Subject to changes

13/17

www.muratamems.fi

Doc.Nr. 8261700

Rev.A3

To obtain the differential digital output value, Dout, RDAY must be subtracted from RDAX.

Dout =

RDAX

– RDAY

The transfer function from differential digital output to angle can be presented as































LSB/g

LSB

LSB

arcsin

0

@

Sens

D

D

out

out



where;

differential digital output (

RDAX

– RDAY)

digital offset value, nominal value = 0 in differential mode



angle

Sens

sensitivity of the device

. (SCA103T-D04: 6554, SCA103T-D05: 3277)

As an example, the following table contains SCA103T-D04 data register values and calculated

differential digital output values with -5, -1 0, 1 and 5 degree tilt angles.

Angle

[°]

Acceleration

[mg]

RDAX

RDAY

DOUT

(RDAX

–RDAY)

-5

-87.16

dec: 739

bin: 010 1110 0011

dec: 1309

bin: 101 0001 1101

dec: -570

-1

-17.45

dec: 967

bin: 011 1100 0111

dec: 1081

bin: 100 0011 1001

dec: -144

0

0

dec: 1024

bin: 100 0000 0000

dec: 1024

bin: 100 0000 0000

dec: 0

1

17.45

dec: 1081

bin: 100 0011 1001

dec: 967

bin: 011 1100 0111

dec: 114

5

87.16

dec: 1309

bin: 101 0001 1101

dec: 739

bin: 010 1110 0011

dec: 570

2.6

Self Test and Failure Detection Modes

To ensure reliable measurement results, the SCA103T has continuous interconnection failure and

calibration memory validity detection. A detected failure forces the output signal close to power

supply ground or VDD level, outside the normal output range. The normal output ranges are:

analog 0.25-4.75 V (@Vdd=5V) and SPI 102...1945 counts.

The calibration memory validity is verified by continuously running parity checks for the control

register memory content. In a case where a parity error is detected the control register is

automatically re-loaded from the EEPROM. If a new parity error is detected after re-loading data

both analog output voltages are forced to go close to ground level (<0.25 V) and SPI outputs goes

below 102 counts.

The SCA103T also includes a separate self test mode. The true self test simulates acceleration, or

deceleration, using an electrostatic force. The electrostatic force simulates acceleration that is high

enough to deflect the proof mass to its extreme positive position, and this causes the output signal

to go to the maximum value. The self test function is activated either by a separate on-off

command on the self test input, or through the SPI.

The self-

test generates an electrostatic force, deflecting the sensing element’s proof mass, thus

checking the complete signal path. The true self test performs following checks:



Sensing element movement check



ASIC signal path check



PCB signal path check