MC33035 Motorola, MC33035 Datasheet - Page 17

• Manufacturer Part Number: MC33035
• Description: BRUSHLESS DC MOTOR CONTROLLER
• Manufacturer: Motorola

controller. This configuration is ideally suited for automotive
and other low voltage applications since there is only one
power switch voltage drop in series with a given stator
winding. Current flow is unidirectional or half wave because
only one end of each winding is switched. Continuous braking
with the typical half wave arrangement presents a motor
overheating problem since stator current is limited only by the
winding resistance. This is due to the lack of upper power
switch transistors, as in the full wave circuit, used to
disconnect the windings from the supply voltage V
MOTOROLA ANALOG IC DEVICE DATA
Figure 38 shows a three phase, three step, half wave motor
R
C
T
T
60 /120
Fwd/Rev
Speed
Set
V
M
Faster
10
22
17
18
11
13
12
6
3
8
4
5
7
Error Amp
Figure 38. Three Phase, Three Step, Half Wave Motor Controller
Reference
Regulator
25 A
Oscillator
PWM
Undervoltage
Lockout
Shutdown
Thermal
Gnd
M
R
R
S
S
Decoder
Position
. A unique
Rotor
Q
Q
16
MC33035
solution is to provide braking until the motor stops and then
turn off the bottom drives. This can be accomplished by using
the Fault Output in conjunction with the Output Enable as an
over current timer. Components R
to give the motor sufficient time to stop before latching the
Output Enable and the top drive AND gates low. When
enabling the motor, the brake switch is closed and the PNP
transistor (along with resistors R
the latch by discharging C
clamped by a single zener and three diodes.
Brake
23
I
Limit
C
DLY
24
1
20
19
14
2
21
9
15
DLY
R
. The stator flyback voltage is
DLY
1
and R
DLY
V
R
R
and C
M
2
1
DLY
) are used to reset
DLY
S
are selected
Motor
N
N
S
17