MC33192 Datasheet, PDF (6/12 Pages) Motorola, Inc – MI-Bus Interface Stepper Motor Controller

Freescale SMeCm33i1c9o2nductor, Inc.
Permanent magnetic stepping motors exhibit the
characteristic ability to hold a shaft rotor position with or
without a stator coil being energized. Normally the shaft
holding ability of the motor with a stator coil energized is
referred to as “Holding Torque” while “Residual Torque” or
“Detent Torque” refers to the shaft holding ability when a
stator coil is not energized. The Holding Torque value is
dependent on the interactive magnetic force created by the
resulting energized stator fields with that of the permanent
magnet rotor. The Residual Torque is a function of the
physical size and composition of the permanent magnet rotor
material coupled with its intrinsic magnetic attraction for the
un–energized stator core material and as a result, the weaker
of the two torques.
It is to be noted when using half step operation, only one
coil is energized during alternate step periods which
produces a somewhat weaker Holding Torque. Holding
Torque is maximized when both coils are simultaneously
energized. In addition, since each winding and resulting flux
conditions are not perfectly matched for each half step,
incremental accuracy is not as good as when full stepping.
Two Phase Drive Signals
The DIR1 and DIR2 bits in the Data Frame of the Push
Field determine the direction of H–Bridge current flow, and
thus the magnetic field polarization of the stator coils, for
H–Bridge outputs “A” and “B” respectively. The directional
signals DIR1 and DIR2, generated by the MCU,
communicate over the MI–Bus to control the two H–Bridge
power output stages of the MC33192 to drive two phase
bipolar permanent magnet motors. Figure 8 shows the
MC33192 truth table to accomplish incremental stepping of
the motor in a clockwise or counter–clockwise direction in
either half or full step modes. The stator field polarization and
rotor position are also shown for reference relative to the
basic stepper motor of Figure 5.
Figure 8. Truth Table and Serial Push Field Data Bits For Sequential Stepping
Push Field Bits
Step
D0 D1 D2 D3 D4
H–Bridge Outputs
Full Half Inh1 DIR1 E DIR2 Inh2 A1 A2 B1 B2
1
1
1
0
1
0
1
1
0
1
0
–
2
1
0
1
X
0
1
0
Z
Z
Stator
Field
(Note 2)
Rotor
Position
(Note 2)
Direction
of Shaft
Rotation
CCW
2
3
1
0
1
1
1
1
0
0
1
–
4
0
X
1
1
1
Z
Z
0
1
3
5
1
1
1
1
1
0
1
0
1
–
6
1
1
1
X
0
0
1
0
0
4
7
1
1
1
0
1
0
1
1
0
CW
–
8
0
X
1
0
1
Z
Z
1
0
0
X
X
X
0
Z
Z
Z
Z
1
1
0
1
1
Z
1
Z
1
1
0
0
0
1
1
Z
1
Z
1
1
0
0
0
Z
1
Z
Z
0
0
0
1
1
Z
Z
Z
1
NOTES: 1. X = Don’t care; Z = High impedance; 1 = High (active “on”) state; 0 = Low (inactive “off”) state.
2. The stator field direction and position of the rotor are shown for explanation purposes and relative to the basic
stepper motor shown in Figure 3.
3. DIR1 establishes the direction of current flow in H–Bridge “A”.
4. DIR2 establishes the direction of current flow in H–Bridge “B”.
6
MOTOROLA ANALOG IC DEVICE DATA
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