MC33033DWR2 View Datasheet(PDF) - ON Semiconductor

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MC33033DWR2

Brushless DC Motor Controller

ON Semiconductor 

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 limited−feature, 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, cycle−by−cycle 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 pull−up

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 pull−up

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

positive−going 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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