COMMON

BRAKE INPUT

LS7262

MOTOR SUPPLY

BRAKE

Vss

OVERCURRENT

SENSE

L4

L3

L2

L1

Vss

FIGURE 4A

5

9

2

4

6

8

12

O1

O3

O4

O6

BRAKE

COMMON

LS7262

OVERCURRENT

SENSE

Vss

Vss

12

5

9

2

4

6

8

L4

L3

L2

L1

BRAKE

MOTOR SUPPLY

O1

O3

O4

O6

FIGURE 4B

Vss

-

+

13

V TRIP

OSCILLATOR

R6

R2

C1

S1

R1

15

Vss

C3

Vss

R3

R4

R5

D1

C2

Vss

R8

LS7260

or

LS7262

FROM MOTOR

POSITION

SENSOR

14

C4

R7

FIGURE 5

CLOSED-LOOP SPEED CONTROLLER

A closed loop system can be configured by differentiating

one of the motor position sense inputs and integrating only

the negative pulses to form a DC voltage that is applied to

the inverting input of an op-amp. The non-inverting input

voltage is adjusted with a potentiometer until the resultant

voltage at VTRIP causes the motor to run at desired speed.

The R2-C1 differentiator, the R3-D1 negative pulse trans-

mitter and the R4-C2 integrator form a frequency to voltage

converter. An increase in motor speed above the desired

speed causes VTRIP to increase which lowers the PWM

and the resultant motor speed. A decrease in speed lowers

VTRIP and raises the PWM and the resultant motor speed.

For proper operation, both R5 and R6 should be greater

than R4, and R4 in turn should be greater than both R2 and

R3. Also, the R4-C2 time constant should be greater than

the R2-C1 time constant. C3 may be added across R6 for

additional VTRIP smoothing.

FIGURE 4. FOUR PHASE OUTPUT DRIVER CIRCUITRY

The information included herein is believed to be

accurate and reliable. However, LSI Computer Systems,

Inc. assumes no responsibilities for inaccuracies, nor for

any infringements of patent rights of others which may

result from its use.

7260-082697-6