PRELIMINARY DATASHEET

May, 2000

4

PRELIMINARY

2

3

4

5

6

9

0

20

9

6

5

4

3

2

ISENSE

TACH

SPEED COMP

RVCO

SPEED SET

RT

HA

HB

HC

VCC

CVCO

SOFT START

SPEED FB

ND

FB C

FB B

FB A

LC

LB

LA

TOP VIEW

ML4435

20-P n PDIP P20

20-P n SOIC S20

ML4435

PIN

NAME

FUNCTION

1

ISENSE

Motor current sense input which triggers pulse by pulse current limit when

ISENSE exceeds 0.55V

2

TACH

A clock output of 6 pulses per commutation cycle when SPEED FB is greater

than 0.97V otherwise the TACH output is at 5V

3

SPEED COMP

Connection node for speed loop compensation components

4

RVCO

Connection node for external resistor to set VCO frequency

5

SPEED SET

DC input for setting motor speed

6

RT

External resistor from this pin to ground controls the IC's PWM timing (frequency)

7

HA

High-side output driver for motor phase A

8

HB

High-side output driver for motor phase B

9

HC

High-side output driver for motor phase C

10

VCC

Power Supply input

11

LA

Low-side output driver signal for motor phase A

12

LB

Low-side output driver signal for motor phase B

13

LB

Low-side output driver signal for motor phase C

14

FB A

Back EMF signal input for motor phase A

15

FB B

Back EMF signal input for motor phase B

16

FB C

Back EMF signal input for motor phase C

17

GND

Signal and power ground

18

SPEED FB

Connection node for back-EMF sensing compensation components

19

SOFT START

Connection node for external soft start capacitor which reduces start up current

20

CVCO

Connection node for external capacitor to set VCO frequency. Forcing this input

below 1.5V causes the commutation to stop and the motor to coast

PIN DESCRIPTIONS

PIN CONFIGURATION