MC33035 Motorola, MC33035 Datasheet - Page 15

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

Three Phase Motor Commutation
full–featured open loop motor controller with full wave, six
step drive. The upper power switch transistors are
Darlingtons while the lower devices are power MOSFETs.
Each of these devices contains an internal parasitic catch
diode that is used to return the stator inductive energy back to
the power supply. The outputs are capable of driving a delta
or wye connected stator, and a grounded neutral wye if split
supplies are used. At any given rotor position, only one top
and one bottom power switch (of different totem poles) is
enabled. This configuration switches both ends of the stator
winding from supply to ground which causes the current flow
to be bidirectional or full wave. A leading edge spike is usually
present on the current waveform and can cause a
current–limit instability. The spike can be eliminated by
adding an RC filter in series with the Current Sense Input.
Using a low inductance type resistor for R
spike reduction. Care must be taken in the selection of the
MOTOROLA ANALOG IC DEVICE DATA
The three phase application shown in Figure 36 is a
R
C
T
60 /120
Fwd/Rev
T
Enable
V
Speed
Set
M
Faster
22
17
18
12
13
10
11
4
5
6
3
7
8
Error Amp
Reference
Regulator
Oscillator
25 A
Figure 36. Three Phase, Six Step, Full Wave Motor Controller
PWM
Undervoltage
Lockout
Shutdown
Thermal
S
Gnd
will also aid in
Decoder
Position
R
S
S
R
Rotor
SYSTEM APPLICATIONS
Q
Q
16
MC33035
bottom power switch transistors so that the current during
braking does not exceed the device rating. During braking,
the peak current generated is limited only by the series
resistance of the conducting bottom switch and winding.
If the motor is running at maximum speed with no load, the
generated back EMF can be as high as the supply voltage,
and at the onset of braking, the peak current may approach
twice the motor stall current. Figure 37 shows the
commutation waveforms over two electrical cycles. The first
cycle (0 to 360 ) depicts motor operation at full speed while
the second cycle (360 to 720 ) shows a reduced speed with
about 50% pulse width modulation. The current waveforms
reflect a constant torque load and are shown synchronous to
the commutation frequency for clarity.
23
Brake
I
Limit
I
peak
14
2
1
24
21
20
19
9
15
+
R
C
switch
Fault
Ind.
V
M
Q
Q
3
)
)
6
R
V
EMF
R
M
Q
Q
2
winding
5
Q
1
Q
R
4
S
A
B
C
S
Motor
N
N
S
15