MC33035 View Datasheet(PDF) - ON Semiconductor
Part Name
Description
Manufacturer
MC33035 Datasheet PDF : 28 Pages
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MC33035, NCV33035
SYSTEM APPLICATIONS
Three Phase Motor Commutation
The three phase application shown in Figure 36 is a
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 RS will also aid in
spike reduction. Care must be taken in the selection of the
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.
Ipeak
+
VM
Rswitch
)
)
EMF
Rwinding
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.
4
5
Fwd/Rev
60°/120°
Enable
VM
6
Rotor
Position
3
Decoder
22
7
25 μA
17
Undervoltage
Lockout
18
Speed
Set
Faster
RT
Reference
Regulator
8
11 Error Amp
12
PWM
13
10
Oscillator
CT
Thermal
Shutdown
R
Q
S
S
Q
R
Gnd 16
Fault VM
14
Ind.
2
Q1
N
AS
S
1
Q2
N
24
Q3
B
C
Motor
ILimit
23
Brake
21
Q4
20
Q5
19
Q6
9
15 C
R
RS
Figure 36. Three Phase, Six Step, Full Wave Motor Controller
http://onsemi.com
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