Datasheet

AD2S1200
Rev. 0 | Page 19 of 24
04406-0-012
1
5
–0
–40
–35
–30
–25
–20
MAGNITUDE (dB)
–15
–10
–5
–45
10 100 10k1k
FREQUENCY (Hz)
100k
Figure 12. RDC System Magnitude Response
04406-0-013
1
0
–20
–180
–160
–140
–120
–100
PHASE (Degrees)
–80
–60
–40
–200
10 100 10k1k
FREQUENCY (Hz)
100k
Figure 13. RDC System Phase Response
04406-0-014
0
20
18
2
4
6
8
10
ANGLE (Degrees)
12
14
16
0
12 43
TIME (ms)
5
Figure 14. RDC Small Step Response
SOURCES OF ERROR
Acceleration
A tracking converter employing a Type II servo loop does not
suffer any velocity lag. There is, however, an error associated
with acceleration. This error can be quantified using the
acceleration constant (K
a
) of the converter.
ErrorTracking
onAcceleratiInput
K
a
=
Conversely,
a
K
onAcceleratiInput
ErrorTracking =
Figure 15 shows tracking error versus acceleration for the
AD2S1200.
The numerator and denominator’s units must be consistent. The
maximum acceleration of the AD2S1200 has been defined as
the acceleration that creates an output position error of 5°
(when LOT is indicated). The maximum acceleration can be
calculated as
2
2
000,103
)/(360
5)(sec
rps
rev
K
onAcceleratiMaximum
a
≅
°
°×
=
−
The AD2S1200 will be able to withstand the maximum
acceleration of 103,000 rps
2
for approximately 10 ms before
reaching its maximum tracking rate of 1,000 rps.
ms
rps
rps
10
)(000,103
)(000,1
2
≅
04406-0-015
0
10
9
1
2
3
4
5
TRACKING ERROR (Degrees)
6
7
8
0
40k 80k 160k120k
ACCELERATION (rps
2
)
200k
Figure 15. Tracking Error vs. Acceleration