DESCRIPTION

Oscillator.

The output current at ROSC pin is mirrored to

COSC pin with a proper direction according to its

voltage slope.

The triangular wave form at COSC pin, being

compared with a threshold, defines the PWM duty

cycle at the motor driver output M+ and M-.

The oscillator also supplies the time base for the

switch off and switch on delays and the Time Out

Counter.

The typical oscillator period is:

Tosc = 7.04 x Rosc x Cosc

February 2001

®

150K

Ω

150K

Ω

OP1

COMP1

+

-

01

0

1

1

2

+

-

COMP7

+

switch on

DELAY

VR7 =

7.5% Vcc

switch off

D ELAY

35V

35V

6.6% Vcc

VR2 =

56.6% Vcc

COMP2

COMP3

I

I

curr.

sense

I

OSCILLATOR

OP8

+

-

VR8 =

14.2% Vcc

COMP4

pwm

DELAY

+

VR4 = 1.5V

COUN TER

RES

TIME OUT

Vcc

Tck

FF

S

R

Vcc

Tck

Vcc

ROSC

GND

M+

M-

VR2=56.6%Vcc

VR3=6.6%Vcc

TEMP.

SENSE

Current ratio = 1 : 2

VR5 = 6.6% Vcc

| 5 Verr|

curr.

limit

curr.

limit

Vcc

Vcc

Vcc

16V

VR2 =

56.6% Vcc

VR3 =

6.6% Vcc

7V

Td_on

Td_pwm

Td_off

10V

open

over

temp.

VOLT.

SENSE

over volt.

over volt.

DELAY 1

Td_ov_1

(130

µs)

Vcc

open

START

Latch

IN

STOP

STOP

START

DIRECTION

PWM

DRIVE R

CONTROL

OFF

OFF

over volt.

D ELAY2

Td_ov_2

(1ms)

Q

curr.

limit

curr.

limit

BLOCK DIAGRAM

MInidip

ORDERING NUMBER: L9909

L9909

DC MOTOR DRIVER WITH POSITION CONTROL

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