AN2785 datasheet(48/51 Pages) STMICROELECTRONICS

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Layout suggestions

AN2785

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Doc ID 14785 Rev 1

Layout suggestions

Typically, for power applications using high voltages and large load currents, the board

layout of all circuits related to the power stage is important. Board layout includes different

aspects, such as track dimensions (length and width), circuit areas, but also the proper

routing of the traces and the optimized reciprocal arrangement of the various system

elements and power sources in the PCB area.

There are several reasons for paying attention to the layout, which include all the EMI

issues, both induced and perceived by the application, over-voltage spikes due to parasitic

inductances along the PCB traces, proper connection of the sense blocks and the logic

inputs of the L6393 device.

Figure 37

provides some layout guidelines and suggestions for a full-bridge application.

Figure 37.

Layout suggestion for a H-bridge power system

As explained in Section 6.1.6, the gate driving PCB traces should be designed as short as

possible and the circuit area should be minimized to avoid sensitivity of such structures to

surrounding noise. Typically, a good power system layout keeps the power IGBTs (or

MOSFETs) of each half-bridge as close as possible to the related gate driver.

Figure 37

shows a set of parasitic inductances related to the different circuit tracks. The

various inductance groups may have undesired effects which should be limited as much as

possible. Moreover, note that Figure 37 emphasizes parasitic inductances located on the

lines usually managing high voltages and fast current transitions, which are very noisy.

HVG

H.V.

OUT

LVG

L6393

LP1

GND

inputs

control signals

MINIMIZE

TO LIMIT

THE BELOW

GROUND SPIKE

ON OUT PIN

POWER GROUND

SIGNAL GROUND

DRIVER GROUND

MINIMIZE TO LIMIT THE NOISE

ON THE INPUT LOGIC SIGNALS AND ON THE

ANALOG OPAMP OUTPUT

NOT CRITICAL

BULK

CAPACITOR

MINIMIZE

THE LENGHT OF

THESE PATHS

(IF USED)

CHOSE RSENSE

WITH LOW

PARASITIC

INDUCTANCE

TRACKS SWITCHING WITH HIGH VOLTAGE

TRANSITIONS SHOULD BE KEPT FAR FROM

THE LOGIC AND SENSING LINES

MINIMIZE

THIS AREA

LP2

LP3

LP4

LP5

phase 1

LP4

L6393

phase 2

LP3

LP2

LP1

LOAD

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