July 2000
ML4423*
1, 2, or 3-Phase Variable Speed AC Motor Controller
GENERAL DESCRIPTION
The ML4423 provides the PWM sinewave drive signals
necessary for controlling three phase AC induction motors as
well as single and two phase split capacitor AC induction
motors.
A constant voltage/frequency ratio can be maintained
over a frequency range of greater than 10:1, providing
15Hz to 150Hz control. The output variable frequency AC
voltages are sensed and fed back to the controller to track the
sinewave frequency and amplitude set at the speed control
input. Direction, on two and three phase motors, is controlled
by changing the relative phase difference between the motor
windings: 90× for two phase motors and 120× and 240× for three
phase motors.
To protect the motor, power devices, high voltage drivers
and control circuitry, the ML4423 includes fixed period,
pulse by pulse variable duty cycle current limit, deadtime
circuitry, and undervoltage lockout. The ML4423 has
selectable output voltage swing of 5V or 12V for
interfacing to different high side drivers and power devices.
FEATURES
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Drives single, two, and three phase AC motors
Greater than 10:1 variable speed control range
Constant V/F ratio with programmable end points
Reverse capability for two and three phase motors
Low distortion PWM sinewave drive
Eliminates run capacitors in PSC motors
Coast function for quick power disable
Low cost interface for various gate drivers
PWM current limit, undervoltage lockout, and
programmable deadtime
12V
±20%
operation with onboard 8V reference
s
(* Indicates Part Is End Of Life As Of July 1, 2000)
BLOCK DIAGRAM
27
SINE A-C
FB A
1
FB C
2
5V/12 SELECT
FB B
3
+
–
+
–
+
–
+
–
28
SINE B-C
13
CT
15
F/R
18
3PH/2PH
COAST
14
PWM
OSCILLATOR
RDT
9
25
HA
PWM
SINE
WAVE
CONTROL
HB
GATING
LOGIC
&
OUTPUT
DRIVERS
HC
LA
LB
LC
24
22
23
21
19
20
16
CO
12
SINE A
GENERATOR
VSPEED
5
VMIN
4
RSPEED
6
SINE C
GENERATOR
UVLO
SPEED
CONTROL
SINE B
GENERATOR
26
VDD
REFERENCE
GND
17
8
RREF
VREF
+
COMP
ISENSE
0.5V
–
7
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
