SCA100T Series
sensor element electrode. This causes the electrostatic force that deflects the beam of the sensing
element and simulates the acceleration to the positive direction. The self-test is de-activated by
giving the MEAS command. The self test function must not be activated for both channels at
the same time.
Self test for Y-channel (STY) activates the self test function for the Y-channel (Channel 2). The
internal charge pump is activated and a high voltage is applied to the Y-channel acceleration
sensor element electrode.
Read X-channel acceleration (RDAX) accesses the AD converted X-channel (Channel 1)
acceleration signal stored in acceleration data register X.
Read Y-channel acceleration (RDAY) accesses the AD converted Y-channel (Channel 2)
acceleration signal stored in acceleration data register Y.
During normal operation, acceleration data registers are reloaded every 150 µs. The load
operation is disabled whenever the CSB signal is low, hence CSB must stay high at least 150 µs
prior the RDAX command in order to guarantee correct data. Data output is an 11-bit digital word
that is fed out MSB first and LSB last.
C SB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
17
18
16
S C K
C O M M A N D
M O S I
M IS O
D A T A O U T
H IG H IM PE D A N C E
9
8
7
6
5
4
3
2
10
1
0
Figure 11. Command and 11 bit acceleration data transmission over the SPI
2.5 Digital Output to Angle Conversion
The acceleration measurement results in RDAX and RDAY data registers are in 11 bit digital word
format. The data range is from 0 to 2048. The nominal content of RDAX and RDAY data registers
in zero angle position are:
Binary: 100 0000 0000
Decimal: 1024
The transfer function from differential digital output to angle can be presented as
D
[
LSB
]
− Dout@0°
LSB
]
⎛
⎜
⎜
⎝
⎞
⎟
⎟
⎠
out
α = arcsin
Sens LSB/g
[
]
where;
Dout
digital output (RDAX or RDAY)
Dout@0° digital offset value, nominal value = 1024
α
Sens
angle
sensitivity of the device. (SCA100T-D01: 1638, SCA100T-D02: 819)
VTI Technologies Oy
www.vti.fi
Subject to changes
Doc. nr. 8261800
12/18
Rev.A
VTI [ VTI TECHNOLOGIES ]
