L6223 datasheet(31/33 Pages) STMICROELECTRONICS

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Figure 36: Peaktransient 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 Rthj-amb. It’s impor-

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.

L6223

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L6223 bảng dữ liệu(PDF) 31 Page - STMicroelectronics