MC33030

http://onsemi.com

9

try to follow and center about the reference voltage setting

if it is within the input common−mode voltage range of

Pin 3; Figures 4 and 5. Initially consider that the feedback

input voltage level is somewhere on the dashed line between

defined above and the motor will be off. Now if the reference

will turn−on [3] enabling Q Drive, causing Drive Output A

to sink and B to source motor current [8]. The actuator will

Comparator B will turn−off, activating the brake enable [4]

and Q Brake [6] causing Drive Output A to go high and B to

go into a high impedance state. The inertia of the mechanical

system will drive the motor as a generator creating a positive

voltage on Pin 10 with respect to Pin 14. The servo system

can be stopped quickly, so as not to over−shoot through the

dead zone range, by braking. This is accomplished by

shorting the motor/generator terminals together. Brake

current will flow into the diode at Drive Output B, through

transistor at Drive Output A. The end of the solid line and

resting position of the actuator after braking.

Inverting

Input

Overvoltage

Monitor

Drive Brake Logic

+

Drive

Output A

Drive

Output B

Motor

10

11

Power

H−Switch

Q Brake

Q Brake

Overcurrent

Monitor

Overcurrent

Reference

15

+

16

Overcurrent

Delay

5.5

mA

7.5 V

Ref.

50 k

R

S

Over−

Current

Latch

Q Drive

S

Q Drive

R

Brake Enable

Direction

Latch

18 V

Ref.

Gearbox and Linkage

GND

4, 5,12,13

+

Window

Detector

Reference

Input Filter

20 k

35

mA

A

B

3.0 k

3.0 k

35

mA

20 k

Non−

Inverting

Input

9

Input

Filter

+

Output

20 k

0.3 mA

8 20 k Error Amp

Error Amp

Output Filter/

Feedback

Input

Figure 17. Representative Block Diagram and Typical Servo Application

14

Q

Q

Q

100 k

2

1

Q

3

6

Reference

Input

7

100 k