L6223A ST Microelectronics, Inc., L6223A Datasheet - Page 31

• Manufacturer Part Number: L6223A
• Description: Dmos Programmable High Speed Unipolar Stepper Motor Driver
• Manufacturer: ST Microelectronics, Inc.

Figure 36: Peak transient Rth pulse width and Duty Cycle.
Notes on the p.c.b. design.
We recommend to observe the following layout
rules to avoid application problems associated
with ground loops and anomalous recirculation
currents. The by-pass capacitors for the power
and logic supply must to be kept as close to the
IC as possible.
It’s important to separate on the PCB board the
logic and the power grounds avoiding that
grounds traces of the logic signals cross the
ground traces of the power signals. The starpoint
grounding, the point of the board in which the
logic ground meets the power ground, should be
kept far enough away from where the power
ground traces terminate to ground (sense resis-
tors and protection zener diodes traces). This
avoids interference with the logic signals. Be-
cause the IC uses the board as a heatsink the
dissipating copper area must be sized in accord-
ance with the required value of R
tant to provide a good filter for the logic supply,
especially for the resistor of the oscillator net-
work. In addition, the capacitor ground of the RC
network must be as clean as possible. When the
ground is used also to heatsink, it is helpful to
use either a polistyrin capacitor or one with a low
temperature coefficient. The value of the boot-
strap capacitor is not a critical parameter, never-
theless the use of a capacitor of 10nF 20% is
recommended. A non-inductive resistor is the
best way to implement the sensing, but when that
is not possible, more metalfilm resistors of the
same value can be paralleled.
thj-amb
. It’s impor-
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