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MC33033PG View Datasheet(PDF) - ON Semiconductor

Part NameDescriptionManufacturer
MC33033PG Brushless DC Motor Controller ON-Semiconductor
ON Semiconductor ON-Semiconductor
MC33033PG Datasheet PDF : 27 Pages
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MC33033, NCV33033
INTRODUCTION
The MC33033 is one of a series of high performance
monolithic dc brushless motor controllers produced by
ON Semiconductor. It contains all of the functions required
to implement a limitedfeature, open loop, three or four
phase motor control system. Constructed with Bipolar
Analog technology, it offers a high degree of performance
and ruggedness in hostile industrial environments. The
MC33033 contains a rotor position decoder for proper
commutation sequencing, a temperature compensated
reference capable of supplying sensor power, a frequency
programmable sawtooth oscillator, a fully accessible error
amplifier, a pulse width modulator comparator, three open
collector top drive outputs, and three high current totem pole
bottom driver outputs ideally suited for driving power
MOSFETs.
Included in the MC33033 are protective features
consisting of undervoltage lockout, cyclebycycle current
limiting with a latched shutdown mode, and internal thermal
shutdown.
Typical motor control functions include open loop speed
control, forward or reverse rotation, and run enable. In
addition, the MC33033 has a 60°/120° select pin which
configures the rotor position decoder for either 60° or 120°
sensor electrical phasing inputs.
FUNCTIONAL DESCRIPTION
A representative internal block diagram is shown in
Figure 19, with various applications shown in Figures 35,
37, 38, 42, 44, and 45. A discussion of the features and
function of each of the internal blocks given below and
referenced to Figures 19 and 37.
Rotor Position Decoder
An internal rotor position decoder monitors the three
sensor inputs (Pins 4, 5, 6) to provide the proper sequencing
of the top and bottom drive outputs. The Sensor Inputs are
designed to interface directly with open collector type Hall
Effect switches or opto slotted couplers. Internal pullup
resistors are included to minimize the required number of
external components. The inputs are TTL compatible, with
their thresholds typically at 2.2 V. The MC33033 series is
designed to control three phase motors and operate with four
of the most common conventions of sensor phasing. A
60°/120° Select (Pin 18) is conveniently provided which
affords the MC33033 to configure itself to control motors
having either 60°, 120°, 240° or 300° electrical sensor
phasing. With three Sensor Inputs there are eight possible
input code combinations, six of which are valid rotor
positions. The remaining two codes are invalid and are
usually caused by an open or shorted sensor line. With six
valid input codes, the decoder can resolve the motor rotor
position to within a window of 60 electrical degrees.
The Forward/Reverse input (Pin 3) is used to change the
direction of motor rotation by reversing the voltage across
the stator winding. When the input changes state, from high
to low with a given sensor input code (for example 100), the
enabled top and bottom drive outputs with the same alpha
designation are exchanged (AT to AB, BT to BB, CT to CB).
In effect the commutation sequence is reversed and the
motor changes directional rotation.
Motor on/off control is accomplished by the Output
Enable (Pin19). When left disconnected, an internal pullup
resistor to a positive source enables sequencing of the top
and bottom drive outputs. When grounded, the Top Drive
Outputs turn off and the bottom drives are forced low,
causing the motor to coast.
The commutation logic truth table is shown in Figure 20.
In half wave motor drive applications, the Top Drive
Outputs are not required and are typically left disconnected.
Error Amplifier
A high performance, fully compensated Error Amplifier
with access to both inputs and output (Pins 9, 10, 11) is
provided to facilitate the implementation of closed loop
motor speed control. The amplifier features a typical dc
voltage gain of 80 dB, 0.6 MHz gain bandwidth, and a wide
input common mode voltage range that extends from ground
to Vref. In most open loop speed control applications, the
amplifier is configured as a unity gain voltage follower with
the Noninverting Input connected to the speed set voltage
source. Additional configurations are shown in Figures 30
through 34.
Oscillator
The frequency of the internal ramp oscillator is
programmed by the values selected for timing components
RT and CT. Capacitor CT is charged from the Reference
Output (Pin 7) through resistor RT and discharged by an
internal discharge transistor. The ramp peak and valley
voltages are typically 4.1 V and 1.5 V respectively. To
provide a good compromise between audible noise and
output switching efficiency, an oscillator frequency in the
range of 20 to 30 kHz is recommended. Refer to Figure 2 for
component selection.
Pulse Width Modulator
The use of pulse width modulation provides an energy
efficient method of controlling the motor speed by varying
the average voltage applied to each stator winding during the
commutation sequence. As CT discharges, the oscillator sets
both latches, allowing conduction of the Top and Bottom
Drive Outputs. The PWM comparator resets the upper latch,
terminating the Bottom Drive Output conduction when the
positivegoing ramp of CT becomes greater than the Error
Amplifier output. The pulse width modulator timing
diagram is shown in Figure 21. Pulse width modulation for
speed control appears only at the Bottom Drive Outputs.
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