April 1997
PRELIMINARY
ML4428
*
Sensorless Smart-StartTM 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.
1
FEATURES
s
Stand-alone operation with forward and reverse
s
On-board start sequence: Sense Position
Drive
Accelerate
Set Speed
s
No backward movement at start-up
s
Patented back-EMF commutation technique
s
Simple variable speed control with on-board reference
s
Single external resistor sets all critical currents
s
PWM control for maximum efficiency or linear control
for minimum noise
s
12V operation provides direct FET drive for 12V motors
s
Drives high voltage motors with high side FET drivers
s
Guaranteed no shoot-through when driving external
FET gates directly
* Some Packages Are End Of Life
BLOCK DIAGRAM/TYPICAL APPLICATION
18
13
22
23
24
2
3
4
10
11
9
9V POWER FAIL
BACK-EMF
SAMPLER
HIGH SIDE
GATE DRIVE
LOW SIDE
GATE DRIVE
VFLT
VCO
PHI1
PHI2
PHI3
P1
P2
P3
N1
N2
N3
28
GND
PWM CURRENT
CONTROL
AND ONE SHOT
1
ISNS
26
CIOS
START-UP
AND
COMMUTATION
LOGIC
17
CSNS
25
BRAKE
8
6V
REF
7
27
PWM
SPEED
CONTROL
VSPEED
VREF
RREF
CPWM
CSC
5
6
VCO
16
15
RVCO
CVCO
20
RCVCO
14
VCC
12
F/R
19
RINIT
CISC
21
+
0.6V
RUN
2
ML4428
PIN CONFIGURATION
ML4428
28-Pin Molded Narrow Dip (P28N)
28-Pin SOIC(S28)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
I
SNS
P1
P2
P3
C
SC
C
PWM
V
REF
V
SPEED
N1
N2
N3
F/R
VCO
V
CC
GND
R
REF
C
IOS
BRAKE
PHI3
PHI2
PHI1
C
ISC
RC
VCO
R
INIT
V
FLT
C
SNS
R
VCO
C
VCO
TOP VIEW
3
ML4428
PIN DESCRIPTION
1
I
SNS
Motor current sense input. Current
limit one-shot is triggered when this
pin is approximately 0.5V.
2
P1
Drives the external P-channel
transistor driving motor PHI1.
3
P2
Drives the external P-channel
transistor driving motor PHI2.
4
P3
Drives the external P-channel
transistor driving motor PHI3.
5
C
SC
The resistor/capacitor combination on
this gm amplifier output sets a pole
zero of the speed loop in conjunction
with a gm of 0.230mmho.
6
C
PWM
A capacitor to ground at this pin sets
the PWM oscillator frequency. A 1nF
capacitor will set the frequency to
approximately 25kHz for PWM speed
control. Grounding this pin selects
linear speed control.
7
V
REF
This voltage reference output (6V) can
be used to set the speed reference
voltage.
8
V
SPEED
This voltage input to the amplifier in
the speed loop controls the speed
target of the motor.
9
N1
Drives the external N-channel
MOSFETs for PHI1.
10 N2
Drives the external N-channel
MOSFETs for PHI2.
11 N3
Drives the external N-channel
MOSFETs for PHI3.
12 F/R
The forward/reverse pin controls the
sequence of the commutation states
and thus the direction of motor
rotation. (TTL level)
13 VCO
This logic output indicates the
commutation frequency of the motor
in run mode. (TTL level)
14 V
CC
12V power supply.
15 C
VCO
Timing capacitor for VCO
16 R
VCO
The resistor on this pin sets a process
independent current to generate a
repeatable VCO frequency.
17 C
SNS
This capacitor to ground sets the ON
time of the 6 sense pulses used for
position detection at start-up and at
low speeds. A 5.6nF capacitor will set
the on time to approximately 200s.
18 V
FLT
A logic "0" indicates the power supply
is under-voltage. (TTL level)
19 R
INIT
This resistor sets the minimum VCO
frequency, and thus, the initial on time
of the drive energization at start-up. A
2 M resistor to ground sets the
minimum VCO frequency to
approximately 10Hz, resulting in an
initial drive energization pulse of
100ms in conjunction with 82nF C
VCO
and 10k R
VCO
.
20 RC
VCO
VCO loop filter components.
21 C
ISC
A capacitor to ground at this gm
amplifier output sets a pole in the
current-mode portion of the speed
loop in conjunction with a gm of
0.230mmho.
22 PHI1
Motor Terminal 1
23 PHI2
Motor Terminal 2
24 PHI3
Motor Terminal 3
25 BRAKE
A "0" activates the braking circuit.
(TTL level)
26 C
IOS
A 50A current from this pin will
charge a timing capacitor to GND for
fixed OFF-time PWM current control
27 R
REF
This resistor sets constant currents on
the device to reduce process
dependence and external components.
A 120k resistor sets the previously
mentioned current levels.
28 GND
Signal and Power Ground
PIN NAME
FUNCTION
PIN NAME
FUNCTION
4
ML4428
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings are those values beyond which
the device could be permanently damaged. Absolute
maximum ratings are stress ratings only and functional
device operation is not implied.
Supply Voltage (pin 14) ............................................. 14V
Output Current (pins 2, 3, 4, 9,10,11) ................... 50mA
Logic Inputs (pins 12, 25) ................................ 0.3 to 7V
Junction Temperature ............................................ 150C
Storage Temperature Range ..................... 65C to 150C
Lead Temperature (Soldering 10 sec.) .................... 260C
Thermal Resistance (
q
JA
)
Plastic DIP ....................................................... 52C/W
Plastic SOIC ..................................................... 75C/W
OPERATING CONDITIONS
Temperature Range
Commercial ............................................... 0C to 70C
Industrial ................................................ 40C to 85C
V
CC
Voltage ..................................................... 12V
10%
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, T
A
= 0C to 70C, V
CC
= 12V, R
SNS
= 0.3, C
VCO
= 82nF, C
IOS
= 100pF,
R
REF
= 120k, C
SNS
= 5.6nF, R
VCO
= 10k, R
INIT
= 2Meg (Notes 1, 2, and 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Oscillator (VCO)
Frequency vs. V
PIN 20
RC
VCO
= 2V
0C to 70C
550
600
750
Hz/V
40C to 85C
520
600
750
Hz/V
Maximum Frequency
RC
VCO
= 6V
0C to 70C
1850
2150
2350
Hz
40C to 85C
1650
2150
2350
Hz
Sampling Amplifier
I
RCVCO
(Note 4)
State A, V
PH2
= VCC/3
80
116
150
A
State A, V
PH2
= VCC/2
25
0
25
A
State A, V
PH2
= 2VCC/3
150
116
80
A
Current Limit
I
SNS
Trip Point
0.45
0.5
0.55
One Shot Off Time
10
13
15
s
Power Fail Detection
Power Fail Trip Voltage
8.0
9.0
V
Hysteresis
300
500
700
mV
Logic Inputs
V
IH
Voltage High
2
V
V
IL
Voltage Low
0.8
V
I
IH
Current High
V
IN
= 2.7V
300
0
A
I
IL
Current Low
V
IN
= 0.4V
400
0
A
Logic Outputs
V
OH
Voltage High
I
OUT
= 0.1mA
3.3
V
V
OL
Voltage Low
I
OUT
= 1mA
0.4
V
5
ML4428
ELECTRICAL CHARACTERISTICS
(Continued)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Output Drivers
V
P
High
I
P
= 10A
V
CC
1.2
V
V
P
Low
0.7
1.2
V
I
p
Low
V
P
= 1V
0C to 70C
2.5
4
6
mA
40C to 85C
1.5
4
6
mA
P Comparator Threshold
V
CC
3.0
V
V
N
High
V
PIN12
= 0V
V
CC
1.2
V
V
N
Low
I
N
= 1mA
0.7
1.2
V
N Comparator Threshold
3
V
Speed Control
f
PWM
C
OSC
= 1nF
20
25
36
kHz
gm Current
160
A
CSC Positive Clamp
2.9
3.1
3.35
V
CISC Positive Clamp
5.2
5.5
5.6
V
CISC Negative Clamp
1.2
1.7
1.9
V
V
REF
5.5
5.9
6.5
V
Supply
V
CC
Current
18
25
32
mA
Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions.
Note 2: F/R and BRAKE have internal 17k
W pull-up resistors to an internal 5V reference.
Note 3: V
FLT
and VCO have internal 4.3k
W pull-up resistors to an internal 5V reference.
Note 4: For explanation of states, see Figure 6 and Table 1.
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