MC33035, NCV33035
14
VCC = 12 V
VBoost VM = 170 V
2
1.0 k
5
Rotor
1
6
Position
Decoder
1 2 1.0 M
4
21
4.7 k
24
1N4744
20
MOC8204
Optocoupler
Load
19
21
20
19
Figure 25. High Voltage Interface with
N−Channel Power MOSFETs
40 k
9
R
Q4
100 mV 15
C
RS
23
Brake Input
The addition of the RC filter will eliminate current−limit instability caused by the
leading edge spike on the current waveform. Resistor RS should be a low in-
ductance type.
Figure 26. Current Waveform Spike Suppression
21
Rg
D
20
Rg
D
19
Rg
D
40 k
9
100 mV 15
23
D = 1N5819
Brake Input
Series gate resistor Rg will dampen any high frequency oscillations caused
by the MOSFET input capacitance and any series wiring induction in the
gate−source circuit. Diode D is required if the negative current into the Bot-
tom Drive Outputs exceeds 50 mA.
Figure 27. MOSFET Drive Precautions
C
21
C
20
C
19
40 k
9
100 mV 15
23
Brake Input
IB
+
0
t
−
Base Charge
Removal
The totem−pole output can furnish negative base current for enhanced tran-
sistor turn−off, with the addition of capacitor C.
Figure 28. Bipolar Transistor Drive
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14