5804
BiMOS II UNIPOLAR
STEPPER-MOTOR
TRANSLATOR/DRIVER
APPLICATIONS INFORMATION
Internal power-on reset (POR) circuitry resets
OUTPUT
A
(and OUTPUT
D
in the two-phase
drive format) to the on state with initial applica-
tion of the logic supply voltage. After reset, the
circuit then steps according to the tables.
The outputs will advance one sequence
position on the high-to-low transition of the STEP
INPUT pulse. Logic levels on the HALF-STEP
and ONE-PHASE inputs will determine the drive
format (one-phase, two-phase, or half-step). The
DIRECTION pin determines the rotation se-
quence of the outputs. Note that the STEP
INPUT must be in the low state when changing
the state of ONE-PHASE, HALF-STEP, or
DIRECTION to prevent erroneous stepping.
All outputs are disabled (off) when OUTPUT
ENABLE is at a logic high. If the function is not
required, OUTPUT ENABLE should be tied low.
In that condition, all outputs depend only on the
state of the step logic.
During normal commutation of a unipolar
stepper motor, mutual coupling between the
motor windings can force the outputs of the
UCN5804B below ground. This condition will
cause forward biasing of the collector-to-substrate
junction and source current from the output. For
many L/R applications, this substrate current is
high enough to adversely affect the logic circuitry
and cause misstepping. External series diodes
(Schottky are recommended for increased
efficiency at low-voltage operation) will prevent
substrate current from being sourced through the
outputs. Alternatively, external ground clamp
diodes will provide a preferred current path from
ground when the outputs are pulled below ground.
Internal thermal protection circuitry disables
all outputs when the junction temperature reaches
approximately 165°C. The outputs are enabled
again when the junction cools down to approxi-
mately 145°C.
Step
POR
1
2
3
4
WAVE-DRIVE SEQUENCE
Half Step = L, One Phase = H
A
ON
ON
OFF
OFF
OFF
B
OFF
OFF
ON
OFF
OFF
C
OFF
OFF
OFF
ON
OFF
D
OFF
OFF
OFF
OFF
ON
TWO-PHASE DRIVE SEQUENCE
Half Step = L, One Phase = L
Step
POR
1
2
3
4
A
ON
ON
ON
OFF
OFF
B
OFF
OFF
ON
ON
OFF
C
OFF
OFF
OFF
ON
ON
D
ON
ON
OFF
OFF
ON
HALF-STEP DRIVE SEQUENCE
Half Step = H, One Phase = L
Step
POR
1
2
3
4
5
6
7
8
A
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
ON
B
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
OFF
C
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
D
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
