April 1997
PRELIMINARY
ML4428*
Sensorless Smart-Start™ BLDC PWM Motor Controller
GENERAL DESCRIPTION
The ML4428 motor controller provides all of the functions
necessary for starting and controlling the speed of delta or
wye-wound Brushless DC (BLDC) Motors without the need
for Hall Effect sensors.
Back-EMF voltage is sensed from the motor windings to
determine the proper commutation phase sequence using
PLL techniques. The patented back-EMF sensing technique
used will commutate virtually any 3-phase BLDC motor that
has at least a 30% variation in inductance during rotation
and is insensitive to PWM noise and motor snubbing
circuitry.
The ML4428 also utilizes a patented start-up technique
which samples the rotor position and applies the proper
drive to accelerate the motor. This ensures no reverse
rotation at start-up and reduces total start-up time.
FEATURES
s
s
Stand-alone operation with forward and reverse
On-board start sequence: Sense Position
Æ
Drive
Æ
Accelerate
Æ
Set Speed
No backward movement at start-up
Patented back-EMF commutation technique
Simple variable speed control with on-board reference
Single external resistor sets all critical currents
PWM control for maximum efficiency or linear control
for minimum noise
12V operation provides direct FET drive for 12V motors
Drives high voltage motors with high side FET drivers
s
s
s
s
s
s
s
s
Guaranteed no shoot-through when driving external
FET gates directly
* Some Packages Are End Of Life
BLOCK DIAGRAM/TYPICAL APPLICATION
19
RINIT
CSC
5
6
CPWM
PWM
SPEED
CONTROL
CISC
RREF
VREF
VSPEED
6V
REF
16
RVCO
VCO
15
CVCO
20
RCVCO
14
VCC
9V POWER FAIL
VCO
13
PHI1
22
BACK-EMF
SAMPLER
PHI2
23
PHI3
24
27
7
8
+
–
RUN
0.6V
HIGH SIDE
GATE DRIVE
P1
2
P2
3
P3
4
F/R
12
BRAKE
25
CSNS
17
26
START-UP
AND
COMMUTATION
LOGIC
PWM CURRENT
CONTROL
AND ONE SHOT
CIOS
1
ISNS
N1
LOW SIDE
GATE DRIVE
N2
N3
11
GND
28
9
10
V
FLT
18
21
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
