AD2S82 AD [Analog Devices], AD2S82 Datasheet - Page 10

• Manufacturer Part Number: AD2S82
• Description: Variable Resolution, Monolithic Resolver-to-Digital Converters
• Manufacturer: AD [Analog Devices]

AD2S81A/AD2S82A
PARAMETER
t
t
t
t
t
t
t
t
t
t
t
t
t
1
2
3
4
5
6
7
8
9
10
11
12
13
ENABLE
SELECT
INHIBIT
RIPPLE
INHIBIT
DATA
BUSY
DATA
BYTE
DATA
CLK
DIR
V
H
V
H
V
H
V
V
Z
T
200
10
470
16
3
70
485
515
–
40
35
60
60
t
L
MIN
7
Figure 3. Digital Timing
t
t
t
6
8
2
V
H
V
V
L
L
V
cos
T
600
25
580
45
25
140
625
670
600
110
110
140
125
H
sin
MAX
t
12
t
4
t
t
V
V
5
10
t
sin
sin
H
L
11
t
1
V
t
t
CONDITION
BUSY WIDTH V
RIPPLE CLOCK V
RIPPLE CLOCK V
BUSY V
BUSY V
INHIBIT V
MIN DIR V
MIN DIR V
INHIBIT V
ENABLE V
ENABLE V
BYTE SELECT V
BYTE SELECT V
t
H
V
9
V
L
L
DIGITAL
MULTIPLIER
Figure 4. AD2S81A/AD2S82A Functional Diagram
H
H
TO DATA V
TO DATA V
H
L
RATIO
H
H
L
L
TO DATA STABLE
TO BUSY V
V
V
TO DATA V
TO DATA V
TO BUSY V
TO BUSY V
H
L
H
L
H
–V
H
L
V
TO DATA STABLE
TO DATA STABLE
TO NEXT BUSY V
TO BUSY V
H
H
H
L
t
A1 sin ( –
13
H
V
t
H
L
H
H
3
L
AC ERROR
DIRECTION
H
V
V
H
L
) sin
CLOCK
H
–10–
t
DEMODULATOR
CIRCUIT FUNCTIONS AND DYNAMIC
PERFORMANCE
The AD2S81A/AD2S82A allows the user greater flexibility in
choosing the dynamic characteristics of the resolver-to-digital
conversion to ensure the optimum system performance. The
characteristics are set by the external components shown in
Figure 1, and the Component Selection section explains how to
select desired maximum tracking rate and bandwidth values.
The following paragraphs explain in greater detail the circuit of
the AD2S81A/AD2S82A and the variations in the dynamic
performance available to the user.
Loop Compensation
The AD2S81A and AD2S82A (connected as shown in Figure
1a and 1b) operates as a type 2 tracking servo loop where the
VCO/counter combination and integrator perform the two inte-
gration functions inherent in a type 2 loop.
Additional compensation in the form of a pole/zero pair is re-
quired to stabilize any type 2 loop to avoid the loop gain charac-
teristic crossing the 0 dB axis with 180 of additional phase lag,
as shown in Figure 6. This compensation is implemented by the
integrator components (R4, C4, R5, C5).
The overall response of such a system is that of a unity gain
second order low pass filter, with the angle of the resolver as the
input and the digital position data as the output.
The AD2S81A/AD2S82A does not have to be connected as
tracking converter, parts of the circuit can be used indepen-
dently. This is particularly true of the Ratio Multiplier which
can be used as a control transformer (see Application Note).
A block diagram of the AD2S81A/AD2S82A is given in
Figure 4.
SENSITIVE
PHASE-
VCO
R4
INTEGRATOR
R6
R5
C4
C5
VELOCITY
REV. B