MC33035 Motorola, MC33035 Datasheet - Page 9

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

decoder can resolve the motor rotor position to within a
window of 60 electrical degrees.
direction of motor rotation by reversing the voltage across the
stator winding. When the input changes state, from high to
low with a given sensor input code (for example 100), the
enabled top and bottom drive outputs with the same alpha
designation are exchanged (A
effect, the commutation sequence is reversed and the motor
changes directional rotation.
(Pin 7). When left disconnected, an internal 25 A current
source enables sequencing of the top and bottom drive
outputs. When grounded, the top drive outputs turn off and
the bottom drives are forced low, causing the motor to coast
and the Fault output to activate.
safety to be designed into the final product. Braking is
accomplished by placing the Brake Input (Pin 23) in a high
state. This causes the top drive outputs to turn off and the
bottom drives to turn on, shorting the motor–generated back
EMF. The brake input has unconditional priority over all other
inputs. The internal 40 k
interfacing with the system safety–switch by insuring brake
activation if opened or disconnected. The commutation logic
truth table is shown in Figure 20. A four input NOR gate is
used to monitor the brake input and the inputs to the three
top drive output transistors. Its purpose is to disable braking
until the top drive outputs attain a high state. This helps to
MOTOROLA ANALOG IC DEVICE DATA
The Forward/Reverse input (Pin 3) is used to change the
Motor on/off control is accomplished by the Output Enable
Dynamic motor braking allows an additional margin of
Output Enable
R
C
T
Forward/Reverse
T
60 /120 Select
V
Reference Output
Error Amp Out
PWM Input
=
in
Sensor
Inputs
Noninv. Input
Sink Only
Positive True
Logic With
Hysteresis
Faster
T
S
S
S
to A
pull–up resistor simplifies
A
C
B
V
V
CC
C
B
22
17
18
13
11
12
10
6
3
7
8
4
5
, B
T
Error Amp
Reference
Regulator
to B
Figure 19. Representative Block Diagram
Oscillator
20 k
25 A
B
, C
PWM
20 k
Undervoltage
40 k
T
Lockout
40 k
to C
20 k
4.5 V
9.1 V
Shutdown
B
Thermal
MC33035
). In
Decoder
Latch
Latch
Position
R
R
S
S
16
Rotor
Q
Q
Gnd
prevent simultaneous conduction of the the top and bottom
power switches. In half wave motor drive applications, the
top drive outputs are not required and are normally left
disconnected. Under these conditions braking will still be
accomplished since the NOR gate senses the base voltage
to the top drive output transistors.
Error Amplifier
access to both inputs and output (Pins 11, 12, 13) is provided
to facilitate the implementation of closed loop motor speed
control. The amplifier features a typical DC voltage gain of
80 dB, 0.6 MHz gain bandwidth, and a wide input common
mode voltage range that extends from ground to V
open loop speed control applications, the amplifier is
configured as a unity gain voltage follower with the
noninverting input connected to the speed set voltage source.
Additional configurations are shown in Figures 31 through 35.
Oscillator
programmed by the values selected for timing components
R
Output (Pin 8) through resistor R
internal discharge transistor. The ramp peak and valley
voltages are typically 4.1 V and 1.5 V respectively. To provide
a good compromise between audible noise and output
switching efficiency, an oscillator frequency in the range of
20 to 30 kHz is recommended. Refer to Figure 1 for
component selection.
T
A high performance, fully compensated error amplifier with
The frequency of the internal ramp oscillator is
and C
23
T
. Capacitor C
Brake Input
40 k
100 mV
T
2
1
14
24
21
20
19
9
15
is charged from the Reference
A
B
C
T
T
T
A
B
C
Current Sense
Reference Input
Current Sense Input
B
B
B
T
V
Bottom
Drive
Outputs
M
and discharged by an
Fault Output
Top
Drive
Outputs
ref
. In most
9