L6219 Datasheet, PDF (4/9 Pages) STMicroelectronics – STEPPER MOTOR DRIVER

L6219
ELECTRICAL CHARACTERISTICS (Continued)
Symbol
PROTECTION
Parameter
Test Condition
T_J
Thermal Shutdown Temperature
Min. Typ. Max. Unit
-
170
-
°C
Figure 1
FUNCTIONAL DESCRIPTION
The circuit is intended to drive both windings of a
bipolar stepper motor.
The peak current control is generated through
switch mode regulation.
There is a choice of three different current levels
with the two logic inputs I01 - I11 for winding 1 and
I02 - I12 for winding 2.
The current can also be switched off completely
Input Logic (I0 and I1)
The current level in the motor winding is selected
with these inputs. (See fig. 2)
If any of the logic inputs is left open, the circuit will
treat it has a high level input.
I₀
I₁
Current Level
H
H
No Current
L
H
Low current V₃ I_O max
H
L
Medium current 2/3 I_O max
L
L
Maximum current IO max
Phase
This input determines the direction of current flow
in the windings, depending on the motor connec-
tions. The signal is fed through a Schmidt-trigger
for noise immunity, and through a time delay in
order to guarantee that no short-circuit occurs in
the output stage during phase-shift.
High level on the PHASE input causes the motor
current flow from Out A through the winding to
Out B
Current Sensor
This part contains a current sensing resistor (RS),
a low pass filter (RC, CC) and three comparators.
Only one comparator is active at a time. It is acti-
vated by the input logic according to the current
level chosen with signals Io and I1.
The motor current flows through the sensing re-
sistor RS.
When the current has increased so that the volt-
age across RS becomes higher than the refer-
ence voltage on the other comparator input, the
comparator goes high, which triggers the pulse
generator.
The max peak current Imax can be defined by:
I_max
=
V_ref
10 R_s
Single-pulse Generator
The pulse generator is a monostable triggered on
the positive going edge of the comparator output.
The monostable output is high during the pulse
time, toff , which is determined by the time compo-
nents Rt and Ct.
toff = 1.1 ⋅ RtCt
The single pulse switches off the power feed to
the motor winding, causing the winding current to
decrease during toff.
If a new trigger signal should occur during toff, it is
ignored.
Output Stage
The output stage contains four Darlington transis-
tors (source drivers) four saturated transistors
(sink drivers) and eight diodes, connected in two
H bridge.
4/9