May 1997
ML4411*/ML4411A**
Sensorless Spindle Motor Controller
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.
The ML4411A includes a comparator on the P3 output to
prevent cross-conduction.
FEATURES
s
s
s
s
s
s
s
Back-EMF commutation provides maximum torque
for minimum “spin-up” time for spindle motors
Accurate, jitter-free phase locked motor speed
feedback output
Linear or PWM motor current control
Easy microcontroller interface for optimized start-up
sequencing and speed control
Power fail detect circuit with delayed braking
Drives external N-channel FETs and P-channel FETs
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* This Product Is Obsolete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
BLOCK DIAGRAM
20
RC
C
VCO
BACK-EMF
SAMPLER
VCO
PH1
PH2
PH3
22
23
24
14
15
16
21
18
26
VCO/TACH OUT
RESET
I
RAMP
ENABLE E/A
BRAKE
DIS PWR
LOGIC
AND
CONTROL
VCC2
POWER
DRIVERS
4
P1-3
3
GATE
DRIVE
6
3
N1-3
BLDC
MOTOR
8
C
BRK
28
27
7
I
CMD
I
LIMIT
PWR FAIL
+5
VCC
LINEAR OR PWM
CURRENT CONTROL
I
SENSE
C
OS
12
PATENTED
13
6
17
19
25
POWER
FAIL
DETECT
C
OTA
GND
1
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
