The L297/A/D Stepper Motor Controller IC gener-
ates four phase drive signals for two phase bipolar
and four phase unipolar step motors in microcom-
puter-controlled applications. The motor can be
driven in half step, normal and wawe drive modes
and on-chip PWM chopper circuits permit switch-
mode control of the current in the windings. A
direction and mode input signals. Since the phase
are generated internally the burden on the micro-
processor, and the programmer, is greatly reduced.
Mounted in DIP20 and SO20 packages, the L297
can be used with monolithic bridge drives such as
the L298N or L293E, or with discrete transistors
The SYNC connections The SYNC connections of all L297s to be
synchronized are connected together and the oscillator
components are omitted on all but one. If an external clock source
is used it is injected at this terminal.
state (ABCD = 0101).
The transistor is open when this signal is active.
When a bipolar bridge is used this signal can be used to ensure
fast decay of load current when a winding is de-energized. Also
used by chopper to regulate load current if CONTROL input is low.
Same functions as INH1.
are brought low.
When low chopper acts on INH1 and INH2; when high chopper
acts on phase lines ABCD.
C and D.
A and B.
determines the peak load current.
on all but one device in synchronized multi - L297 configurations. f
Physical direction of motor rotation also depends on connection
Synchronized internally therefore direction can be changed at any
one increment. The step occurs on the rising edge of this signal.
when low selects full step operation. One-phase-on full step mode
is obtained by selecting FULL when the L297's translator is at an
Two-phase-on full step mode is set by selecting FULL when the
translator is at an odd numbered position. (The home position is
designate state 1).
translator to the home position (state 1, ABCD = 0101).
driver, quad darlington array or discrete power
devices in step motor driving applications. It re-
ceives step clock, direction and mode signals from
the systems controller (usually a microcomputer
chip) and generates control signals for the power
The principal functions are a translator, which gen-
erates the motor phase sequences, and a dual
PWM chopper circuit which regulates the current in
the motor windings.The translator generatesthree
different sequences, selected by the HALF/FULL
input. These are normal (two phases energised),
wave drive (one phase energised) and half-step
(alternately one phase energised/two phases en-
ergised). Two inhibit signals are also generated by
the L297 in half step and wave drive modes. These
signals, which connect directly to the L298'senable
inputs, are intended to speed current decay when
a winding is de-energised. When the L297 is used
to drive a unipolar motor the chopper acts on these
An input called CONTROL determines whether the
chopper will act on the phase lines ABCD or the
inhibit lines INH1 and INH2. When the phase lines
(AB or CD) is activated (rather than interrupting the
line then active).In L297 + L298 configurationsthis
technique reduces dissipation in the load current
per.It suppliespulses at the chopper rate which set
the two flip-flops FF1 and FF2. When the current in
a winding reaches the programmed peak value the
voltage across the sense resistor (connected to
one of the sense inputs SENS
oscillator pulse arrives. The peak current for both
windingsis programmedby a voltage divideron the
can be avoided by synchronising the chopper os-
cillators. This is done by connecting all the SYNC
pins together, mounting the oscillator RC network
on one device only and grounding the OSC pin on
all other devices.
for normal drive, wave drive and half step modes.
The state sequences and output waveforms for
these three modes are shown below. In all cases
the translator advances on the low to high transis-
tion of CLOCK.
tation the sequences are simply reversed RESET
restores the translator to state 1, where ABCD =
Half step mode is selected by a high level on the HALF/FULL input.
Normal drive mode (also called "two-phase-on" drive) is selected by a low level on the HALF/FULL input
when the translator is at an odd numbered state (1, 3, 5 or 7). In this mode the INH1 and INH2 outputs
remain high throughout.