Datasheet ML4428CP, ML4428CS, ML4428IP, ML4428IS Datasheet (Micro Linear Corporation)

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.

BLOCK DIAGRAM/TYPICAL APPLICATION

16 15

R

VCO

VCO

C

VCO

RUN

PWM CURRENT

CONTROL

AND ONE SHOT

5

6

21

27

7

8

12

25

C

SC

C

PWM

C

ISC

R

REF

V

REF

V

SPEED

F/R

BRAKE

19

6V

REF

R

INIT

PWM

SPEED

CONTROL

START-UP

COMMUTATION

LOGIC

AND

FEATURES

■ 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

■ Guaranteed no shoot-through when driving external

FET gates directly

* Some Packages Are End Of Life

20

RC

VCO

+
–

0.6V

14

V

CC

9V POWER FAIL

BACK-EMF

SAMPLER

HIGH SIDE

GATE DRIVE

LOW SIDE

GATE DRIVE

V

FLT

VCO

PHI1

PHI2

PHI3

P1

P2

P3

N1

N2

N3

18

13

22

23

24

2

3

4

9

10

11

17

C

SNS

26

C

IOS

I

SNS

1

GND

28

1

ML4428

PIN CONFIGURATION

ML4428

28-Pin Molded Narrow Dip (P28N)

28-Pin SOIC(S28)

C

V

I

SNS

C

PWM

V

REF

SPEED

N1

N2

N3

F/R

VCO

V

1

2

P1

3

P2

4

P3

5

SC

6

7

8

9

10

11

12

13

14

CC

28

GND

27

R

REF

26

C

IOS

25

BRAKE

24

PHI3

23

PHI2

22

PHI1

21

C

ISC

20

RC

VCO

19

R

INIT

18

V

FLT

17

C

SNS

16

R

VCO

15

C

VCO

TOP VIEW

2

PIN DESCRIPTION

PIN NAME FUNCTION PIN NAME FUNCTION

ML4428

1I

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.

5C

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.

6C

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.

7V

REF

This voltage reference output (6V) can
be used to set the speed reference
voltage.

8V

SPEED

This voltage input to the amplifier in
the speed loop controls the speed
target of the motor.

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 200µs.

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 Mý 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

20 RC
21 C

ISC

VCO

and 10k R
VCO loop filter components.
A capacitor to ground at this gm

VCO

.

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

VCO

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
15 C

CC

VCO

12V power supply.

Timing capacitor for VCO

23 PHI2 Motor Terminal 2
24 PHI3 Motor Terminal 3
25 BRAKE A ”0” activates the braking circuit.

(TTL level)

26 C

IOS

A 50µA 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

3

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.

OPERATING CONDITIONS

Temperature Range

Commercial ...............................................0°C to 70°C

Industrial................................................–40°C to 85°C

VCC Voltage..................................................... 12V ±10%

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 ............................................ 150°C

Storage Temperature Range ..................... –65°C to 150°C

Lead Temperature (Soldering 10 sec.) .................... 260°C

Thermal Resistance (qJA)

Plastic DIP .......................................................52°C/W

Plastic SOIC..................................................... 75°C/W

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, TA = 0°C to 70°C, V
R

= 120ký, C

REF

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Oscillator (VCO)

Sampling Amplifier

Current Limit

Power Fail Detection

Logic Inputs

V

IH

V

IL

I

IH

I

IL

Logic Outputs

V

OH

V

OL

= 5.6nF, R

SNS

Frequency vs. V

Maximum Frequency RC

I

(Note 4) State A, V

RCVCO

I

Trip Point 0.45 0.5 0.55

SNS

One Shot Off Time 10 13 15 µs

Power Fail Trip Voltage 8.0 9.0 V
Hysteresis 300 500 700 mV

Voltage High 2 V
Voltage Low 0.8 V
Current High V
Current Low V

Voltage High I
Voltage Low I

PIN 20

VCO

= 10k, R

INIT

RC

State A, V
State A, V

OUT

OUT

= 12V, R

CC

SNS

= 0.3ý, C

VCO

= 82nF, C

IOS

= 100pF,

= 2Meg (Notes 1, 2, and 3)

= 2V 0°C to 70°C 550 600 750 Hz/V

VCO

–40°C to 85°C 520 600 750 Hz/V

= 6V 0°C to 70°C 1850 2150 2350 Hz

VCO

–40°C to 85°C 1650 2150 2350 Hz

= VCC/3 80 116 150 µA

PH2

= VCC/2 –25 0 25 µA

PH2

= 2VCC/3 –150 –116 –80 µA

PH2

= 2.7V –300 0 µA

IN

= 0.4V –400 0 µA

IN

= –0.1mA 3.3 V
= 1mA 0.4 V

4

ML4428

ELECTRICAL CHARACTERISTICS (Continued)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Output Drivers

VP High IP = –10µA VCC – 1.2 V

VP Low 0.7 1.2 V

Ip Low VP = 1V 0°C to 70°C 2.5 4 6 mA

–40°C to 85°C 1.5 4 6 mA

P Comparator Threshold VCC – 3.0 V

Speed Control

Supply

VN High V
VN Low IN = 1mA 0.7 1.2 V
N Comparator Threshold 3V

f

PWM

gm Current ±160 µA
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

VCC Current 18 25 32 mA

= 0V VCC – 1.2 V

PIN12

C

= 1nF 20 25 36 kHz

OSC

5.5 5.9 6.5 V

Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions.
Note 2: F/R and BRAKE have internal 17kW pull-up resistors to an internal 5V reference.
Note 3: V
Note 4: For explanation of states, see Figure 6 and Table 1.

and VCO have internal 4.3kW pull-up resistors to an internal 5V reference.

FLT

5

ML4428

FUNCTIONAL DESCRIPTION

The ML4428 provides closed-loop commutation for
3-phase brushless motors. To accomplish this task, a VCO,
integrating back-EMF Sampling error amplifier and
sequencer form a phase-locked loop, locking the VCO to
the back-EMF of the motor. The IC contains circuitry to
control motor speed in PWM mode. Braking and power
fail detection functions are also provided on the chip. The
ML4428 is designed to drive external power transistors
(N-channel sinking transistors and P-channel sourcing
transistors) directly.

The ML4428 limits the motor current with a constant off­time PWM controlled current. The velocity loop is
controlled with an on-board amplifier. An accurate, jitter­free VCO output is provided equal to the commutation
frequency of the motor. The ML4428 switches the gates of
external N-channel power MOSFETs to regulate the motor
current and directly drives the P-channel MOSFETs for
12V motors. The ML4428 ensures that there is no shoot
through in any state of power drive to the FETs. Higher
voltage motors can be driven using buffer transistors or
standard “high side” drivers.

Speed sensing is accomplished by monitoring the output
of the VCO, which will be a signal which is phase-locked
to the commutation frequency of the motor.

BACK-EMF SENSING AND COMMUTATOR
The ML4428 contains a patented back-EMF sensing circuit

(Figure 1) which samples the phase which is not energized
(Shaded area in Figure 2) to determine whether to increase
or decrease the commutator (VCO) frequency. A late
commutation causes the error amplifier to charge the filter

(RC) on R
commutation causes R
speed control loop uses R

, increasing the VCO input while early

CVCO

to discharge. The analog

CVCO

as a speed feedback

CVCO

voltage.
The input impedance of the three PH inputs is about

8.7ký to GND. When operating with a higher voltage
motor, the PH inputs should be divided down in voltage
with series resistors so that the maximum voltage at any
PH input does not exceed VCC.

NEUTRAL

0 60 120 180 240 0300

Figure 2. Typical Motor Phase Waveform with back-EMF

Superimposed (Ideal Commutation).

PHI1

PHI2

PHI3

22

23

24

5.8K

2.9K

NEUTRAL

SIMULATOR

ΦA + ΦB + ΦC

9

MULTIPLEXER

Va – Vb

I(RC) =

4.35K

SIGN

CHANGER

COMMUTATION

LOGIC

a

+

b

–

RC

VCO

LOOP FILTER

VCO

R

C1

C2

VCO

Figure 1. Back-EMF Sensing Block Diagram

6

ML4428

COMPONENT SELECTION GUIDE
In order to properly select the critical components for the

ML4428 you should know the following things:

1. The motor operating voltage, V

MOTOR

(V).

2. The maximum operating current for the motor,
I

(A).

MAX

3. The number of poles the motor has, N.

4. The back-EMF constant of the motor, Ke (V ¥ s/rad).

5. The torque constant of the motor, Ke (N ¥ m/A). (This
is the same as the back-EMF constant, only in
different units.)

6. The maximum desired speed of operation, RPM

MAX

(rpm).

7. Line to line resistance, R

8. Line to line inductance, L

(Ohms).

L-L

(Henries).

L-L

9. The motor should have at least 15% line-to-line
inductance variation during rotation for proper start­up sensing. (Air core motors will not run using the
ML4428.) Examine the motor to determine if there is
any iron in the core. If the stator coils are not wound
around an iron form, the ML4425 or ML4426 may be
a better choice.

If you do not know one or more of the above values, it is
still possible to pick components for the ML4428, but some
experimentation may be necessary to determine the
optimal value. All quantities are in SI units unless other
wise specified. The formulas in the following section are
based on linear system models. The following formulas
should be considered a starting point from which you can
optimize your application.

Note: Refer to Application Note 43 for details on loop
compensation.

R

SENSE

The function of R

is to provide a voltage proportional

SENSE

to the motor current, for current limit/feedback purposes.
The trip voltage across R

R

I

is the maximum motor current.

MAX

The power dissipation in the resistor is I
R

, so the resistor should be sized appropriately. For

SENSE

SENSE

SENSE

is 0.5V so:

05.

=

I

MAX

squared times

MAX

very high current motors, a smaller resistor can be used,
with an op-amp to increase the gain, so that power
dissipation in the sense resistor is minimized.

RES1, RES2 and RES3
Operating motors at greater than 12V requires attenuation

resistors in series with the sense inputs (PHI1, PHI2, PHI3)
to keep the voltage less than 12V. The phase sense input
impedance is 8700ý. This requires the external resistor to
be set as follows and results in the given attenuation.

RES1 = RES2 = RES3

RESI = 725 (V

Atten

=

RES

MOTOR

2900

+

1 8700

– 10)

A larger value for RES1 may be required if the peak motor
phase voltage exceds V

I

FILTER

SENSE

The I

filter consists of an RC lowpass filter in series with

SENSE

MOTOR

.

the current sense signal. The purpose of this filter is to filter
out noise spikes on the current, which may cause false
triggering of the one shot circuit. It is important that this filter
not slow down the current feedback loop, or destruction of
the output stage may result. The recommended values for
this circuit are R = 1Ký and C= 300pF. This gives a time
constant of 300ns, and will filter out spikes of shorter
duration. These values should suffice for most applications.
If excessive noise is present on the I

pin, the capacitor

SENSE

may be increased at the expense of speed of current loop
response. The filter time constant should not exceed 500ns
or it will have a significant impact on the response speed of
the one shot current limit.

C

IOS

The one shot capacitor determines the off time after the
current limit is activated, i.e. the voltage on the I

SENSE

pin
exceeded 0.5V. The following formula ensures that the
motor current is stable in current limit:

−

11

should be. Higher

IOS

C

is in Farads

IOS

CV

IOS MAX MOTOR()

.=× ×

111 10

This is the maximum value that C
average torque during the current limit cycle can be
achieved by reducing this value experimentally, while
monitoring the motor current carefully, to be sure that a
runaway condition does not occur. This runaway
condition occurs when the current gained during the on
time exceeds the current lost during the off time, causing
the motor current to increase until damage occurs. For
most motors this will not occur, as it is usually a self
limiting phenomenon. (See Figure 7)

7

ML4428

C

VCO

As given in the section on the VCO and phase detector:

C

VCO

2931 10

=

N RPM

×

MAX

−

6

×

Where N is the number of poles in the motor, and RPM is
the motor’s maximum operating speed in revolutions per
minute.

C

PWM

This capacitor sets the PWM ramp oscillator frequency.
This is the PWM “switching frequency”. If this value is too
low, <20kHz, then magnetostriction effects in the motor
may cause audible noise. If this frequency is too high,
>30kHz, then the switching losses in the output drivers
may become a problem. 25kHz should be a good
compromise for this value, which can be obtained by
using a 1nF capacitor.

R

AND R

VCO

R

should be 10k and R

VCO

REF

should be 120k for normal

REF

operation.

VCO FILTER
See the section on the VCO and Phase detector for

information on these components.

VCO AND PHASE DETECTOR CALCULATIONS
The VCO should be set so that at the maximum frequency

of operation (the running speed of the motor) the VCO
control voltage will be no higher than V

, or 6V. The

REF

VCO maximum frequency will be:

F N RPM

=××005.

MAX MAX

where N is the number of poles on the motor and
RPM

is the maximum motor speed in Revolutions Per

MAX

Minute.
The minimum VCO gain derived from the specification

table (using the minimum F

K

VCO MIN

()

Assuming that the V

C

VCO(MAX)

=

VCO

at V

VCO

=

VCO

.

×

2 665 10

C

VCO

= 5.5V, then

××

5 5 2 665 10

..

F

MAX

= 6V) is:

−

5

−

5

or

−

6

×

C

VCO

2931 10

=

×

N RPM

MAX

ROTOR

PHASE

K

VCO

Ω

RC

VCO

(Hz/sec/V)

Z

RC

VCO

C1

(R × C2 × s + 1)

s × (C2 + R × C1 × s × C2 + C1)

LOOP FILTER

2.665 × 10

–5

C

× s

VCO

VCO

SAMPLED

PHASE

Ke × ω × Atten

F

BEMF

SAMPLER

2 × π

PHASE DETECTOR

Gm = 0.23m

+

–

OUT

A/RADIAN

gm = 0.23mA/V

Figure 4. Back-EMF Phase Locked Loop Components.

R

C2

V/A

RADIAN/sec/V

× 2 × π

8

ML4428

3000

2500

2000

1500

FREQUENCY (Hz)

1000

500

0

024681012

Figure 3. VCO Output Frequency vs. V

CVCO = 82nF

CVCO = 164nF

VVCO (VOLTS)

VCO

(Pin 20)

Figure 4 shows the linearized transfer function of the
Phase Locked Loop with the phase detector formed from
the sampled phase through the Gm amplifier with the
loop filtered formed by R, C1, and C2. The Phase detector
gain is:

−

Ke Atten

××

ω

π2

23 10

./

××

4

A Radian

Where Ke is the motor back-E.M.F. constant in V/Radian/
sec, w is the rotor speed in r/s, and Atten is the back­E.M.F. resistive attenuator, nominally 0.3.

The simplified impedance of the loop filter is

Zs

()

RC

1

=

Csss

1

LEAD

ω

()

+

LAG

ω

()

+

Where the lead and lag frequencies are set by:

1

=

ω

ω

LEAD

LAG

RC

CC

+

12

=

RC C

2

12

Requiring the loop to settle in 20 PLL cycles with

w

= 10 ¥ w

LAG

produces the following calculations

LEAD

for R, C1 and C2:

4

7 508 10

.

=

C

1

R

=

Atten K RPM

−

×× ×

Atten K

N

C

= 9 ¥ C

2

889 10

××

1

4

×

.

e MAX

e

where Ke is the back-EMF constant in volts per radian per
second, and RPM

is the rotor speed. See Micro Linear

MAX

application note 35 for derivation of the above formulas.
The 80k resistor to GND from the RC

pin assists in a

VCO

smooth transition from sense mode to closed loop
operation.

I

MOTOR

I

MOTOR

SENSE ~3ms

~200µs

DRIVE ~100ms

t

LOOP CLOSED HERE

(RUN MODE)

DRIVESENSE DRIVESENSE DRIVE DRIVESENSE

Figure 5. Typical Sensed Start-up

t

9

ML4428

C

SNS

A capacitor to ground at this pin sets the ON time of the 6
current sense pulses used for position detection at start-up
and at low speeds. The ON time is set by:

TON = C

Referring to Figure 5, each of the 6 current sense pulses is
governed by a rise time with a time constant of L/R where L
is the inductance of the motor network with 2 windings
shorted and R is the total resistance in series with the motor
between the supply rails. R includes the ON-resistance of
the power-FETs and R

SNS

should match that of the low side FET. L is a function of
rotor position. Each pulse will have a peak value
V

SENSEPEAK

of

VR

SENSEPEAK SNS

=−

where

RRRR

=× +×

075 2

()

L L SDON SENSE

−

(35.7k)

SNS

. The R

DSON

V

MOTOR

R

of the high side FET

−

T




1







ON

/

LR



e





+

What is important for sensing rotor position is the
amplitude difference between each of the three pairs of
current sense pulses. This can be seen by triggering on
I

on an oscilloscope with the RC

SNS

pin shorted to

VCO

ground. One should see the current waveform of Figure 5.
Allowing the peak current sense pulse to reach an
amplitude of 0.5V (by adjusting C

, and hence TON) or,

SNS

allowing the difference between the maximum and
minimum of the 6 pulses to be >50mV, should suffice for
adequate rotor position sensing. A good starting value for
TON is 200µs, requiring C

R

INIT

= 5.6nF.

SNS

The initial time interval between sample pulses during
start-up is set by R
while the RC

VCO

. This time interval (t

INIT

pin is less than 0.25 volts.

t

343.

R

INIT

=

C

INIT

VCO

INIT

) occurs

LL

=×

075..

DIRECTION OUTPUTS INPUT SAMPLES

STATE REVERSE N3 N2 N1 P3 P2 P1

FORWARD N1 N2 N3 P1 P2 P3 FORWARD REVERSE

A OFF OFF ON ON OFF OFF PH2 PH2

B OFF OFF ON OFF ON OFF PH1 PH3

C ON OFF OFF OFF ON OFF PH3 PH1

D ON OFF OFF OFF OFF ON PH2 PH2

E OFF ON OFF OFF OFF ON PH1 PH3

F OFF ON OFF ON OFF OFF PH3 PH1

LL

−

Table 1. Commutation States.

3.75V

C

VCO

2.0V

10

VCO OUT

ABCDEFA

Figure 6. Commutation Timing and Sequencing.

ML4428

START-UP SEQUENCING
When the motor is initially at rest, it is generating no

back-EMF. Because a back-EMF signal is required for
closed loop commutation, the motor must be started by
other means until a velocity sufficient to generate some
back-EMF is attained.

Start
For RC

voltages of less than 0.6V the ML4428 will

VCO

send 6 sample pulses to the motor to determine the rotor
position and drive the proper windings to produce desired
rotation. This will result in motor acceleration until the
RC

pin achieves 0.6V and closed loop operation

VCO

begins. This technique results in zero reverse rotation and
minimizes start-up time. The sample time pulses are set by
C

and the initial sample interval is set by R

SNS

INIT

. This
sense technique is not effective for air core motors, since a
minimum of 30% inductance difference must occur when
the motor moves.

Direction
The direction of motor rotation is controlled by the

commutation states as given in Table 1. The state
sequence is controlled by the F/R.

Run
When the RC

pin exceeds 0.6V the device will enter

VCO

run mode. At this time the motor speed should be about
8% FRPM

and be high enough to generate a

MAX

detectable BEMF and allow closed loop operation to
begin. The commutation position compensation has been
previously discussed.

Speed Control
The speed control section of the ML4428 is detailed in

Figure 8. The two transconductance amplifiers with
outputs at CSC and C

each have a gm of 0.23mmhos.

ISC

The bandwidth of the current feedback component of the
speed control is set at C

f

=

dB

3

For f

= 50kHz, C

3dB

as follows:

ISC

45

23 102366 10

ISC

−−

×

..

π

CC

ISC ISC

would be 730pF. The filter

=

×

components on the CSC pin set the dominant pole in the
system and should have a bandwidth of about 10% of the
position filter on the RC

pin. Typically this is in the 1

VCO

to 10Hz range.

60

50

40

(µs)

30

OFF

T

20

10

The motor will continue to accelerate as long as the
voltage on the RC

is less than the voltage on V

VCO

SPEED

During this time the motor will receive full N-channel
drive limited only by I
approaches that of V

. As the voltage on RC

LIMIT

the C

SPEED

ISC

capacitor will charge

VCO

and begin to control the gate drive to the N-channel
transistor by setting a level for comparison on the 25kHz
PWM saw tooth waveform generated on C
compensation of the speed loop is accomplished on C
and on C
amplifiers with a gm = 2.3 ¥ 10

which are outputs of transconductance

ISC

V

SPEED

RC

C

VCO

I

SNS

PWM

8

20

1

6

–4

ý

.

LEVEL
SHIFT
+1.4V

0.23mmho

+

–

PWM

. The

C

SC

SC

5

.

+

–

0.23mmho

0

0 100 200 300 400 500

Note: 100pF gives 10µs, 200pF gives 20µs, etc.

Slope

Figure 7. I

C

ISC

21

+

–

dTCdV

LIMIT

MODE

SELECT

C

(pF)

IOS

5

V

100 Ω

k===

=

50

i

A

µ

Output Off-Time vs. COS.

LINEAR CONTROL
TO LOW-SIDE
GATE DRIVE

PWM CONTROL
TO COMMUTATION
LOGIC

Figure 8. Speed Control Block Diagram.

11

ML4428

OUTPUT DRIVERS
The P-channel drivers are emitter follower type with 5mA

pull down currents. The N-channel drivers are totem pole
with a 1200ý resistor in series with the pull up device.
Crossover comparators are employed with each driver
pair, eliminating the potential of crossover, and hence,
shoot-through currents.

BRAKING
When BRAKE is pulled low all 3 P-channel drivers will be

turned off and all 3 N-channel drivers will be turned on.

POWER FAIL
In the event of a power fail, i.e. VCC falls below 8.75V all

6 output drivers will be turned off.

HIGHER VOLTAGE MOTOR DRIVE
The ML4428 can be used to drive higher voltage motors

by means of level shifters to the high side drive transistors.
This can be accomplished by using dedicated high side
drivers for applications greater than 80V or a simple NPN
level shift as shown in Figure 9 for applications below
80V. Figure 10 shows how to interface to the IR2118, high
side drivers from I.R. This allows driving motors up to
600V. The BRAKE pin can be pulsed prior to startup with
an RC circuit. This charges the bootstrap capacitors for
three inexpensive high side drivers

12

ML4428

2MΩ

IRFR9120

MOTOR

IRFR120

28

1

300pF

1kΩ

120kΩ

27

GND

ML4428

SNS

I

2

2kΩ

R

P1

REF

2kΩ

RUN

26

IOS

C

P2

3

100pF

25

BRAKE

P3

4

2kΩ

RES1

24

PHI3

CSC

5

50kΩ

0.1µF

BRAKE

RES1

80kΩ

10µF

1µF

21

ISC

C

8

2kΩ

20

VCO

RC

N1N2N3

9

RES1

23

22

PHI2

PHI1

PWMVREFVSPEED

C

6

7

1nF

1µF

100Ω

100Ω

SPEED CONTROL VOLTAGE

19

INIT

R

10

100Ω

PWR FAIL

18

17

FLT

SNS

V

C

F/R

11

12

16

15

VCOCVCO

R

VCO

V

13

14

VCO

5.6nF

10kΩ

0.1µF

750pF

CC

0.1µF

+12V

0.1µF

MOTOR

V

+24 TO

0.1µF

60V

2kΩ 2kΩ 2kΩ

330µF

Q3

IRFR9120

Q2

IRFR9120

Q1

+12V

2N6718

0.1µF

IRFR120

2N6718

IRFR120

1kΩ

2N6718

0.1µF

Figure 9. Driving Higher Voltage Motors: 24V to 80V.

20kΩ

1.5kΩ

FWD/REVERSE

13

ML4428

V

MOTOR

+12V

25V

0.1µF

25V

0.1µF

25V

0.1µF

MUR150

1

2

3

4

MUR150

1

2

3

4

MUR150

1

2

3

4

IR2118

V

CC

IN

COM

N/C

IR2118

V

CC

IN

COM

N/C

IR2118

V

CC

IN

COM

N/C

VB

HO

N/C

VB

HO

N/C

VB

HO

N/C

330µF

IRF720IRF720IRF720

8

7

6

VS

5

100Ω

25V

2.2µF

400V

MOTOR

PH1

8

7

6

VS

5

8

7

6

VS

5

100Ω

25V

2.2µF

100Ω

25V

2.2µF

PH3

PH2

Note: Refer to IK2118 data sheet for
complete information on using
this part with different FETs
and IGBTs.

V

SPEED

0.1µF

100Ω

787Ω

FWD/REVERSE

IRF720 IRF720 IRF720

100Ω

100Ω

1kΩ

0.01µF

10µF

10kΩ

25V

1µF

+12V

12kΩ

VCO

330pF

1nF

0.1µF

ML4428

1

I

SNS

2

P1

3

P2

4

P3

5

CSC

6

C

PWM

7

V

REF

8

V

SPEED

9

N1

10

N2

11

N3

12

F/R

13

VCO

14

V

CC

GND

R

C

BRAKE

PHI3

PHI2

PHI1

C

RC

VCO

R

INIT

V

C

R

VCO

C

VCO

REF

OS

ISC

FLT

SNS

R

SENSE

300MΩ

10W

28

120kΩ

27

26

0.01µF

25

24

23

22

21

20

19

18

17

16

15

750pF

0.01µF

5.11kΩ

5.11kΩ

5.11kΩ

10kΩ

5.6nF

2MΩ

2kΩ

10µF

RUN

BRAKE

PWR FAIL

80kΩ

1µF

14

Figure 11. ML4428 High Voltage Motor Driver: 12V to 500V

PHYSICAL DIMENSIONS inches (millimeters)

Package: P28N

28-Pin Narrow PDIP

1.355 - 1.365

(34.42 - 34.67)

28

ML4428

0.180 MAX
(4.57 MAX)

0.125 - 0.135
(3.18 - 3.43)

PIN 1 ID

1

0.045 - 0.055
(1.14 - 1.40)

0.015 - 0.021
(0.38 - 0.53)

0.100 BSC

(2.54 BSC)

SEATING PLANE

0.280 - 0.296
(7.11 - 7.52)

0.020 MIN

(0.51 MIN)

0.299 - 0.325
(7.60 - 8.26)

0º - 15º

0.008 - 0.012
(0.20 - 0.31)

15

ML4428

PHYSICAL DIMENSIONS inches (millimeters)

0.699 - 0.713

28

(17.75 - 18.11)

Package: S28

28-Pin SOIC

0.024 - 0.034
(0.61 - 0.86)

(4 PLACES)

0.090 - 0.094
(2.28 - 2.39)

0.291 - 0.301
(7.39 - 7.65)

PIN 1 ID

1

0.050 BSC

(1.27 BSC)

0.012 - 0.020
(0.30 - 0.51)

0.095 - 0.107
(2.41 - 2.72)

SEATING PLANE

0.398 - 0.412

(10.11 - 10.47)

0.005 - 0.013
(0.13 - 0.33)

0º - 8º

0.022 - 0.042
(0.56 - 1.07)

0.009 - 0.013
(0.22 - 0.33)

ORDERING INFORMATION

PART NUMBER TEMPERATURE RANGE PACKAGE

ML4428CP (EOL) 0°C to 70°C 28-Pin DIP (P28N)
ML4428CS (EOL) 0°C to 70°C 28-Pin SOIC (S28)

ML4428IP –40°C to 85°C 28-Pin DIP (P28N)
ML4428IS –40°C to 85°C 28-Pin SOIC (S28)

© Micro Linear 1997 is a registered trademark of Micro Linear Corporation
Products described in this document may be covered by one or more of the following patents, U.S.: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940;
5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; Japan: 2598946; 2619299. Other patents are pending.

Micro Linear reserves the right to make changes to any product herein to improve reliability, function or design.
Micro Linear does not assume any liability arising out of the application or use of any product described herein,
neither does it convey any license under its patent right nor the rights of others. The circuits contained in this
data sheet are offered as possible applications only. Micro Linear makes no warranties or representations as to
whether the illustrated circuits infringe any intellectual property rights of others, and will accept no responsibility
or liability for use of any application herein. The customer is urged to consult with appropriate legal counsel
before deciding on a particular application.

16

2092 Concourse Drive

San Jose, CA 95131

Tel: [phone]

Fax: [phone]

DS4428-01