AD2S80A

REV. A

–12–

12

–12

–6

–9

0

–3

3

6

9

FREQUENCY

Figure 4. AD2S80A Gain Plot

180

–180

–90

–135

0

–45

45

90

135

FREQUENCY

Figure 5. AD2S80A Phase Plot

OUTPUT

POSITION

TIME

Figure 6. AD2S80A Small Step Response

The small signal step response is shown in Figure 6. The time

t

1

f

BW

t

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 po-

sition 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

K

Input Acceleration

Error in Output Angle

The numerator and denominator must have consistent angular

may be specified in degrees/sec

Angular measurement may also be specified using radians, min-

utes of arc, LSBs, etc.

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

× K

2

given input acceleration. For example for an acceleration of

100 revs/sec

Error in LSBs

=

=

2.7

= 0.15 LSBs or 47.5 seconds of arc

used to define the dynamics of the converter the following

should be used.

4.04

+C5)

Where n = resolution of the converter.

R4, R6 in ohms

C5, C4 in farads