May 1997

Sensorless Spindle Motor Controller

The ML4411A includes a comparator on the P3 output to

prevent cross-conduction.

FEATURES

s

Back-EMF commutation provides maximum torque

for minimum “spin-up” time for spindle motors

s

Accurate, jitter-free phase locked motor speed

feedback output

s

Linear or PWM motor current control

s

Easy microcontroller interface for optimized start-up

sequencing and speed control

s

Power fail detect circuit with delayed braking

s

Drives external N-channel FETs and P-channel FETs

s

Back-EMF comparator detects motor rotation after

power fail for fast re-lock after brownout

* This Product Is Obsolete

** This Product Is End Of Life As Of August 1, 2000

GENERAL DESCRIPTION

The ML4411 provides complete commutation for delta or

wye wound Brushless DC (BLDC) motors without the need

for signals from Hall Effect Sensors. This IC senses the

back EMF of the three motor windings (no neutral

required) to determine the proper commutation phase

angle using Phase Lock Loop techniques. This technique

will commutate virtually any 3-phase BLDC motor and is

insensitive to PWM noise and motor snubbing. The

ML4411 is architecturally similar to the ML4410 but with

improved braking and brown-out recovery circuitry.

Included in the ML4411 is the circuitry necessary for a

Hard Disk Drive microcontroller driven control loop.

The ML4411 controls motor current with either a constant

off-time PWM or linear current control driven by the

microcontroller. Braking and Power Fail are also included

in the ML4411.

The timing of the start-up sequencing is determined by the

micro, allowing the system to be optimized for a wide

range of motors and inertial loads.

The ML4411 modulates the gates of external N-Channel

power MOSFETs to regulate the motor current. The IC

drives P-Channel MOSFETs directly.

BLOCK DIAGRAM

BLDC

MOTOR

POWER

DRIVERS

GATE

DRIVE

LOGIC

AND

CONTROL

BACK-EMF

SAMPLER

VCO

LINEAR OR PWM

CURRENT CONTROL

POWER

FAIL

DETECT

RC

VCO/TACH OUT

RESET

ENABLE E/A

BRAKE

DIS PWR

PWR FAIL

+5

VCC

GND

3

N1-3

3

P1-3

VCC2

PH3

PH2

PH1

6

PATENTED

20

14

15

16

21

18

26

8

28

27

17

19

25

22

23

24

4

7

12

13

6

1

1