MC33033 Datasheet, PDF (11/24 Pages) ON Semiconductor – BRUSHLESS DC MOTOR CONTROLLER

MC33033
Figure 19. Three Phase, Six Step Commutation Truth Table (Note 1)
Inputs (Note 2)
Outputs (Note 3)
Sensor Electrical Phasing (Note 4)
Top Drives
Bottom Drives
60°
120°
Current
SA SB SC SA SB SC
F/R
Enable Sense AT BT CT AB BB CB
1
0
0
1
0
0
1
1
0
0
1
1
0
0
1
1
1
0
1
1
0
1
1
0
1
0
1
0
0
1
1
1
1
0
1
0
1
1
0
1
0
1
1
0
0
0
1
1
0
1
1
1
1
0
1
1
0
1
0
0
0
0
1
0
0
1
1
1
0
1
1
0
0
1
0
0
0
0
1
0
1
1
1
0
0
1
1
0
1
0
1
0
0
1
0
0
0
1
0
1
1
0
1
0
0
1
1
0
1
1
0
0
1
0
1
1
0
0
1
0
1
1
1
0
1
0
0
1
0
0
1
1
0
1
0
0
1
1
0
1
1
0
1
0
0
1
1
0
0
1
0
0
1
0
0
1
0
1
0
1
0
1
0
0
1
0
0
0
1
0
1
0
1
0
1
0
1
1
0
0
1
0
1
1
1
1
X
X
X
1
1
1
0
0
0
0
1
0
0
0
0
X
X
X
1
1
1
0
0
0
V
V
V
V
V
V
X
0
X
1
1
1
0
0
0
V
V
V
V
V
V
X
1
1
1
1
1
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.
oscillator ramp–up period. The stator current is converted to
a voltage by inserting a ground–referenced sense resistor RS
(Figure 34) in series with the three bottom switch transistors
(Q4, Q5, Q6). 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:
+ RS
0.1
Istator(max)
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.
Reference
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 21. A 6.25 V reference level
was chosen to allow implementation of the simpler NPN
circuit, where Vref – VBE 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
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 (VCC) is monitored to a threshold of 8.9 V.
This level ensures sufficient gate drive necessary to attain
low RDS(on) when interfacing with standard power MOSFET
devices. When directly powering the Hall sensors from the
reference, improper sensor 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.
MOTOROLA ANALOG IC DEVICE DATA
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