
7
Data Device Corporation
www.ddc-web.com
SD-14620
J-04/03-0
-12
dB/oct
GAIN = 4
BA
2A
-6 dB/oct
10B
ω (rad/sec)
2A
2 2 A
ω (rad/sec)
f
= BW =
3dB
2 A (Hz)
π
CLOSED LOOP
OPEN LOOP
- GAIN = 0.4
(B=A/2)
(CRITICALLY DAMPED)
FIGURE 6. BODE PLOTS
ERROR PROCESSOR
INPUT
(
θ)
VELOCITY
OUT
DIGITAL
POSITION
OUT (
φ)
VCO
CT
S
A
+ 1
1
B
S
+ 1
10B
H = 1
+
-
e
A2
S
2
S
A
+1
(
)
B
2
S
+1
(
)
10B
Open Loop Transfer Function =
WHERE:
2
A = A A
1
2
FIGURE 5. TRANSFER FUNCTION BLOCK DIAGRAM
DYNAMIC PERFORMANCE
A type II servo loop (Kv =
∞) and very high acceleration con-
stants give the SD-14620 superior dynamic performance.
TRANSFER FUNCTION AND BODE PLOT
The dynamic performance of the converter can be determined
tion block diagram (FIGURE 5), and its Bode Plots (open and
closed loop - FIGURE 6). Values for the transfer function block
can be obtained from TABLE 4.
The open loop transfer function is as follows:
where A is the gain coefficient
and B is the frequency of lead compensation
ACCURACY AND RESOLUTION
TABLE 5 lists the total accuracy including quantification of the
various resolutions and accuracy grades.
2
S
A
+1
(
)
B
2
S
+1
(
)
10B
Open Loop Transfer Function =
TABLE 4. DYNAMIC CHARACTERISTICS
DEVICE TYPE
60 Hz
“S” OPTION
EACH CHANNEL
Input Frequency
Bandwidth (Closed Loop)
Ka
A1
A2
A
B
Hz
1/s2
1/s
47 - 5K
15
830
0.17
5K
29
14.5
1K - 5K
150
110K
2.47
44.4K
333
166
RESOLUTION
BITS
16
14
12
10
16
14
12
10
Tracking Rate (rps)
typical
minimum
Acceleration ( 1 LSB lag)
Settling Time (179° step max)
rps
deg/s2
msec
0.5
0.4
11.3
2500
2
1.6
45
1100
8
6.4
180
500
32
25.6
720
400
2.5
2
610
232
10
8
2440
150
40
32
9760
78
160
128
39K
51
400 Hz
360 - 5K
56
53K
0.41
41K
130
81
16
14
12
10
2.5
2
93
360
10
8
372
180
40
32
1490
100
160
128
5950
90
TABLE 5. ACCURACY/RESOLUTION
VERSION
RESOLUTION (minutes)
10 BIT
12 BIT
14 BIT
16 BIT
SD-1462X-XX
ACCURACY
(minutes)
±4 +1 LSB
±2 +1 LSB
42.2
10.5
5.3
3.3
4.3
2.3
SD-1462X-XS
(“S” option)
* 1.3 minute accuracy available for “S” option only.
Inclusive of 1 bit of jitter.
±4 +1 LSB
±2 +1 LSB
±1 +1 LSB
25.1
23.1
22.1
9.3
7.3
6.3
5.3
3.3
2.3
4.3
2.3
* 1.3