MC33033, NCV33033
operation can result if the reference output voltage should
fall below 4.5 V. If one or both of the comparators detects an
undervoltage condition, the top drives are turned off and the
Bottom Drive Outputs are held in a low state. Each of the
comparators contain hysteresis to prevent oscillations when
crossing their respective thresholds.
V
in
MPS
U01A
14
REF
7
UVLO
Capacitor C
T
Error Amp Out/
PWM Input
Current Sense
Input
Latch Set"
Inputs
To
Control
Sensor
Power Circuitry
≈5.6
V 6.25 V
V
in
36
14
REF
7
0.1
To Control Circuitry
and Sensor Power
6.25 V
The NPN circuit is recommended for powering Hall or opto sensors,
where the output voltage temperature coefficient is not critical. The PNP
circuit is slightly more complex, but also more accurate. Neither circuit
has current limiting.
UVLO
Top Drive
Outputs
Bottom Drive
Outputs
MPS
U51A
Figure 21. PWM Timing Diagram
Figure 22. Reference Output Buffers
V
M
V
CC
= 12 V
2
Rotor
Position
Decoder
A
T
1
B
T
20
C
T
Load
17
17
V
CC
Q
1
Q
2
Q
3
Rotor
Position
Decoder
2
A
T
1
B
T
20
C
T
1.0 k
1
2
4.7 k
1N4744
MOC8204
Optocoupler
V
Boost
V
M
= 170 V
5
4
6
1.0 M
Load
16
Q
4
16
15
15
Transistor Q
1
is a common base stage used to level shift from V
CC
to the high
motor voltage, V
M
. The collector diode is required if V
CC
is present while V
M
is low.
Figure 23. High Voltage Interface with
NPN Power Transistors
Figure 24. High Voltage Interface with
N−Channel Power MOSFETs
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