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參數資料
| 型號： | 05F6700 |
| 英文描述： | IC-R/D CONVERTER |
| 中文描述： | 集成電路的R / D轉換器 |
| 文件頁數： | 4/16頁 |
| 文件大小： | 187K |
| 代理商： | 05F6700 |
AD2S80A
REV. B
–12–
180
–180
PHASE
PLOT
fBW
–90
–135
0.04fBW
0.02fBW
0
–45
45
90
135
0.4fBW
0.2fBW
0.1fBW
FREQUENCY
2fBW
Figure 5. AD2S80A Phase Plot
OUTPUT
POSITION
TIME
t2
t1
Figure 6. AD2S80A Small Step Response
The small signal step response is shown in Figure 6. The time
from the step to the first peak is t1 and the t2 is the time from
the step until the converter is settled to 1 LSB. The times t1 and
t2 are given approximately by
t
1 =
1
f
BW
t
2 =
5
f
BW
×
R
12
where R = resolution, i.e., 10, 12, 14, or 16.
The large signal step response (for steps greater than 5 degrees)
applies when the error voltage exceeds the linear range of the
converter.
Typically the converter will take 3 times longer to reach the first
peak for a 179 degrees step.
In response to a velocity step, the velocity output will exhibit the
same time response characteristics as outlined above for the
position output.
ACCELERATION ERROR
A tracking converter employing a Type 2 servo loop does not
suffer any velocity lag, however, there is an additional error due
to acceleration. This additional error can be defined using the
acceleration constant KA of the converter.
K
A =
Input Acceleration
Error in Output Angle
The numerator and denominator must have consistent angular
units. For example if KA is in sec
–2, then the input acceleration
may be specified in degrees/sec
2 and the error output in degrees.
Angular measurement may also be specified using radians, min-
utes of arc, LSBs, etc.
KA does not define maximum input acceleration, only the error due
to it’s acceleration. The maximum acceleration allowable before
the converter loses track is dependent on the angular accuracy
requirements of the system.
Angular Accuracy
× KA = Degrees/sec2
KA can be used to predict the output position error for a
given input acceleration. For example for an acceleration of
100 revs/sec
2, K
A = 2.7
× 106 sec–2 and 12-bit resolution.
Error in LSBs
=
Input acceleration [LSB/sec2 ]
K A[sec –2]
=
100 [rev/sec 2 ]
× 212
2.7
×106
= 0.15 LSBs or 47.5 seconds of arc
To determine the value of KA based on the passive components
used to define the dynamics of the converter the following
should be used.
K A
=
4.04
×1011
2n R6 R4 (C4
+C5)
Where n = resolution of the converter.
R4, R6 in ohms
C5, C4 in farads
12
–12
–6
–9
0.04fBW
0.02fBW
0
–3
3
6
9
0.4fBW
0.2fBW
0.1fBW
FREQUENCY
GAIN
PLOT
2fBW
fBW
Figure 4. AD2S80A Gain Plot
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