MC33033, NCV33033
Inputs (Note 2)
Sensor Electrical Phasing (Note 4)
60°
S
A
1
1
1
0
0
0
1
1
1
0
0
0
1
0
V
V
S
B
0
1
1
1
0
0
0
1
1
1
0
0
0
1
V
V
S
C
0
0
1
1
1
0
0
0
1
1
1
0
1
0
V
V
S
A
1
1
0
0
0
1
1
1
0
0
0
1
1
0
V
V
120°
S
B
0
1
1
1
0
0
0
1
1
1
0
0
1
0
V
V
Current
S
C
0
0
0
1
1
1
0
0
0
1
1
1
1
0
V
V
F/R
1
1
1
1
1
1
0
0
0
0
0
0
X
X
X
X
Enable
1
1
1
1
1
1
1
1
1
1
1
1
X
X
0
1
Sense
0
0
0
0
0
0
0
0
0
0
0
0
X
X
X
1
A
T
0
1
1
1
1
0
1
1
0
0
1
1
1
1
1
1
B
T
1
0
0
1
1
1
1
1
1
1
0
0
1
1
1
1
Outputs (Note 3)
Top Drives
C
T
1
1
1
0
0
1
0
0
1
1
1
1
1
1
1
1
Bottom Drives
A
B
0
0
1
1
0
0
1
0
0
0
0
1
0
0
0
0
B
B
0
0
0
0
1
1
0
1
1
0
0
0
0
0
0
0
C
B
1
1
0
0
0
0
0
0
0
1
1
0
0
0
0
0
(Note 5)
F/R = 1
(Note 5)
F/R = 0
(Note 6)
(Note 7)
(Note 8)
NOTES:
1. V = Any one of six valid sensor or drive combinations.
X = Don’t care.
2. The digital inputs (Pins 3, 4, 5, 6, 18, 19) are all TTL compatible. The current sense input (Pin 12) has a 100 mV threshold with respect to Pin 13. A
logic 0 for this input is defined as < 85 mV, and a logic 1 is > 115 mV.
3. The top drive outputs are open collector design and active in the low (0) state.
4. With 60°/120° (Pin 18) in the high (1) state, configuration is for 60° sensor electrical phasing inputs. With Pin 18 in the low (0) state, configuration is
for 120° sensor electrical phasing inputs.
5. Valid 60° or 120° sensor combinations for corresponding valid top and bottom drive outputs.
6. Invalid sensor inputs; All top and bottom drives are off.
7. Valid sensor inputs with enable = 0; All top and bottom drives are off.
8. Valid sensor inputs with enable and current sense = 1; All top and bottom drives are off.
Figure 20. Three Phase, Six Step Commutation Truth Table (Note 1)
Current Limit
Reference
Continuous operation of a motor that is severely
over−loaded results in overheating and eventual failure.
This destructive condition can best be prevented with the use
of cycle−by−cycle current limiting. That is, each on−cycle
is treated as a separate event. Cycle−by−cycle current
limiting is accomplished by monitoring the stator current
build−up each time an output switch conducts, and upon
sensing an over current condition, immediately turning off
the switch and holding it off for the remaining duration of
oscillator ramp−up period. The stator current is converted to
a voltage by inserting a ground−referenced sense resistor R
S
(Figure 35) in series with the three bottom switch transistors
(Q
4
, Q
5
, Q
6
). The voltage developed across the sense
resistor is monitored by the current sense input (Pin 12), and
compared to the internal 100 mV reference. If the current
sense threshold is exceeded, the comparator resets the lower
latch and terminates output switch conduction. The value for
the sense resistor is:
R
+
S
I
0.1
stator(max)
The on−chip 6.25 V regulator (Pin 7) provides charging
current for the oscillator timing capacitor, a reference for the
Error Amplifier, and can supply 20 mA of current suitable
for directly powering sensors in low voltage applications. In
higher voltage applications it may become necessary to
transfer the power dissipated by the regulator off the IC. This
is easily accomplished with the addition of an external pass
transistor as shown in Figure 22. A 6.25 V reference level
was chosen to allow implementation of the simpler NPN
circuit, where V
ref
− V
BE
exceeds the minimum voltage
required by Hall Effect sensors over temperature. With
proper transistor selection, and adequate heatsinking, up to
one amp of load current can be obtained.
Undervoltage Lockout
The dual−latch PWM configuration ensures that only one
single output conduction pulse occurs during any given
oscillator cycle, whether terminated by the output of the
Error Amplifier or the current limit comparator.
A dual Undervoltage Lockout has been incorporated to
prevent damage to the IC and the external power switch
transistors. Under low power supply conditions, it
guarantees that the IC and sensors are fully functional, and
that there is sufficient Bottom Drive Output voltage. The
positive power supply to the IC (V
CC
) is monitored to a
threshold of 8.9 V. This level ensures sufficient gate drive
necessary to attain low R
DS(on)
when interfacing with
standard power MOSFET devices. When directly powering
the Hall sensors from the reference, improper sensor
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