MC33035 Motorola, MC33035 Datasheet - Page 11

• Manufacturer Part Number: MC33035
• Description: BRUSHLESS DC MOTOR CONTROLLER
• Manufacturer: Motorola

Reference
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
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
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
supplies to the IC (V
monitored by separate comparators that have their
thresholds at 9.1 V. This level ensures sufficient gate drive
necessary to attain low R
MOSFET devices. When directly powering the Hall sensors
from the reference, improper sensor operation can result if
the reference output voltage falls below 4.5 V. A third
comparator is used to detect this condition. If one or more of
the comparators detects an undervoltage condition, the Fault
Output is activated, the top drives are turned off and the
bottom drive outputs are held in a low state. Each of the
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 is also more accurate over temperature. Neither circuit has
current limiting.
MOTOROLA ANALOG IC DEVICE DATA
The on–chip 6.25 V regulator (Pin 8) provides charging
A triple Undervoltage Lockout has been incorporated to
Figure 22. Reference Output Buffers
To Control Circuitry
and Sensor Power
V
V
U51A
U01A
MPS
MPS
in
in
Sensor
Power
6.25 V
ref
5.6 V
– V
39
CC
Circuitry
) and the bottom drives (V
Control
6.25 V
BE
0.1
To
DS(on)
17
18
17
18
8
exceeds the minimum voltage
8
when driving standard power
REF
REF
UVLO
UVLO
C
) are each
MC33035
comparators contain hysteresis to prevent oscillations when
crossing their respective thresholds.
Fault Output
provide diagnostic information in the event of a system
malfunction. It has a sink current capability of 16 mA and
can directly drive a light emitting diode for visual indication.
Additionally, it is easily interfaced with TTL/CMOS logic for
use in a microprocessor controlled system. The Fault
Output is active low when one or more of the following
conditions occur:
between motor start–up or sustained operation in an
overloaded condition. With the addition of an RC network
between the Fault Output and the enable input, it is possible
to create a time–delayed latched shutdown for overcurrent.
The added circuitry shown in Figure 23 makes easy starting
of motor systems which have high inertial loads by providing
additional starting torque, while still preserving overcurrent
protection. This task is accomplished by setting the current
limit to a higher than nominal value for a predetermined time.
During an excessively long overcurrent condition, capacitor
C
threshold to a low state. A latch is then formed by the positive
feedback loop from the Fault Output to the Output Enable.
Once set, by the Current Sense Input, it can only be reset by
shorting C
Drive Outputs
collector NPN transistors capable of sinking 50 mA with a
minimum breakdown of 30 V. Interfacing into higher voltage
applications is easily accomplished with the circuits shown in
Figures 24 and 25.
21) are particularly suited for direct drive of N–Channel
MOSFETs or NPN bipolar transistors (Figures 26, 27, 28
and 29). Each output is capable of sourcing and sinking up
to 100 mA. Power for the bottom drives is supplied from V
(Pin 18). This separate supply input allows the designer
added flexibility in tailoring the drive voltage, independent of
V
driving power MOSFETs in systems where V
than 20 V so as to prevent rupture of the MOSFET gates.
inverting input (Pin 15) must return on separate paths to the
central input source ground.
Thermal Shutdown
the IC in the event the maximum junction temperature is
exceeded. When activated, typically at 170 C, the IC acts
as though the Output Enable was grounded.
CC
DLY
The open collector Fault Output (Pin 14) was designed to
1) Invalid Sensor Input code
2) Output Enable at logic [0]
3) Current Sense Input greater than 100 mV
4) Undervoltage Lockout, activation of one or more of
5) Thermal Shutdown, maximum junction temperature
This unique output can also be used to distinguish
The three top drive outputs (Pins 1, 2, 24) are open
The three totem pole bottom drive outputs (Pins 19, 20,
The control circuitry ground (Pin 16) and current sense
Internal thermal shutdown circuitry is provided to protect
. A zener clamp should be connected to this input when
will charge, causing the enable input to cross its
the comparators
being exceeded
DLY
or cycling the power supplies.
CC
is greater
11
C