SCA61T Series
Subject to changes 13/17
www.murata.com Doc. nr. 8261900 Rev.A3
[ ] [ ]
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−
=
°
LSB/g
LSBLSB
arcsin
0@
Sens
DD
outout
a
where;
D
out
digital output (RDAX)
D
out@0°
digital offset value, nominal value = 1024
a
angle
Sens
sensitivity of the device. (SCA61T-FAHH1G: 1638, SCA61T-FA1H1G: 819)
As an example following table contains data register values and calculated differential digital output
values with -5, -1 0, 1 and 5 degree tilt angles.
dec: 881
bin: 011 0111 0001
dec: 953
bin: 011 1011 1001
dec: 995
bin: 011 1110 0011
dec: 1010
bin: 011 1111 0010
dec: 1024
bin: 100 0000 0000
dec: 1024
bin: 100 0000 0000
dec: 1053
bin: 100 0001 1101
dec: 1038
bin: 100 0000 1110
dec: 1167
bin: 100 1000 1111
dec: 1095
bin: 100 0100 0111
2.6 Self Test and Failure Detection Modes
To ensure reliable measurement results the SCA61T 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 check for the control
register memory content. In the 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 voltage is forced to go close to ground level (<0.25 V) and SPI outputs goes
below 102 counts.
The SCA61T 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 the 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
• Micro controller A/D and signal path check
The created deflection can be seen in both the SPI and analogue output. The self test function is
activated digitally by a STX command, and de-activated by a MEAS command. Self test can be
