Vss

-

+

13

V TRIP

EXT. OSCILLATOR

R6

R2

C1

S1

R1

15

Vss

C3

Vss

R3

R4

R5

D1

C2

Vss

R8

LS7362

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 V TRIP 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 V TRIP to increase which lowers the duty cy-

cle modulation of the oscillator and the resultant motor

speed. A decrease in speed lowers V TRIP and raises the

duty cycle modulation 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 V TRIP smoothing.

BRAKE

MOTOR

SUPPLY

Vss

O6

8

5

COMMON

BRAKE

INPUT

7

O4

6

9

O5

LS7362

FIGURE 3.

SINGLE-ENDED

DRIVER CIRCUIT

This configuration requires only

one base current limiting resistor

connected from the COMMON

pin to Vss.

FORWARD

REVERSE

IN914

2.2K

Inputs form SG1731

or UC1637

F/R

LS7362

ENABLE

19

10

FIGURE 4. PRECISION CONTROL

BRUSHLESS DC MOTOR DRIVE

For controlled acceleration and deceleration of motors

in the forward or reverse directions, a motor control

pulse width modulator circuit such as the SG1731 or

UC1637 can be interfaced with the LS7362.

The logical OR gate made up of the resistor-diode net-

work permits the LS7362 to be enabled when either the

forward or reverse input is high. By applying the forward

input directly to Pin 19, the motor can only operate in the

forward direction when the forward input is high and only

in the reverse direction when the reverse input is high.

Motor direction is determined by relative pulse widths of

the forward and reverse inputs while acceleration or

deceleration is determined by variations of these widths.

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.

7362-101992-5