MC33033 Motorola, MC33033 Datasheet - Page 23

• Manufacturer Part Number: MC33033
• Description: BRUSHLESS DC MOTOR CONTROLLER
• Manufacturer: Motorola

Brush Motor Control
dc motors, it may also be used to control dc brush–type
motors. Figure 44 shows an application of the MC33033
driving a H–bridge affording minimal parts count to operate a
brush–type motor. Key to the operation is the input sensor
code [100] which produces a top–left (Q 1 ) and a bottom–right
(Q 3 ) drive when the controller’s Forward/Reverse pin is at
logic [1]; top–right (Q 4 ), bottom–left (Q 2 ) drive is realized
when the Forward/Reverse pin is at logic [0]. This code
supports the requirements necessary for H–bridge drive
accomplishing both direction and speed control.
width modulated frequency of approximately 25 kHz. Motor
speed is controlled by adjusting the voltage presented to the
noninverting input of the Error Amplifier establishing the
PWM s slice or reference level. Cycle–by–cycle current
limiting of the motor current is accomplished by sensing the
voltage (100 mV threshold) across the R S resistor to ground
of the H–bridge motor current. The over current sense circuit
makes it possible to reverse the direction of the motor, on the
MOTOROLA ANALOG IC DEVICE DATA
Though the MC33033 was designed to control brushless
The controller functions in a normal manner with a pulse
10 k
10 k
0.005
FWR/REV
+12 V
Enable
Faster
0.1
18
19
14
10
11
4
5
6
3
7
9
8
Error Amp
Reference
Regulator
Oscillator
PWM
Figure 44. H–Bridge Brush–Type Controller
Undervoltage
Shutdown
Thermal
Decoder
R
S
S
R
Position
13
Rotor
Lockout
Q
Q
Gnd
MC33033
fly, using the normal Forward/Reverse switch, and not have to
completely stop before reversing.
LAYOUT CONSIDERATIONS
circuits on wire–wrap or plug–in prototype boards. High
frequency printed circuit layout techniques are imperative to
prevent pulse jitter. This is usually caused by excessive noise
pick–up imposed on the current sense or error amp inputs.
The printed circuit layout should contain a ground plane with
low current signal and high drive and output buffer grounds
returning on separate paths back to the power supply input
filter capacitor V M . Ceramic bypass capacitors (0.01
connected close to the integrated circuit at V CC , V ref and
error ampliflier noninverting input may be required depending
upon circuit layout. This provides a low impedance path for
filtering any high frequency noise. All high current loops
should be kept as short as possible using heavy copper runs
to minimize radiated EMI.
Do not attempt to construct any of the motor control
I Limit
17
16
20
15
12
2
1
0.001
DC Brush
Motor
22
1.0 k
1.0 k
Q 1 *
Q 2 *
22
M
1.0 k
+12 V
R S
Q 4 *
Q 3 *
23
F)