文档介绍：olwP-or einGieie o oetCO M aito AN-389 Radiation EMI CMOS Lowest for Guidelines Design PC-Board Follow
Fairchild Semiconductor
Follow PC-Board Design Application Note 389
Guidelines for Lowest January 1985
CMOS EMI Radiation
The application of such high-speed CMOS-logic circuits as the 54HC/74HC family (pared with CD4000 metal-gate
logic) requires special attention to pc-board design to minimize conducted and radiated noise.
The need to reduce a logic system’s noise emission is be- noise. An easy empirical method that can serve as a general
coming ever more apparent with the increased use of rule is to render the pc board as optically opaque as possible
high-speed electronics, and with the progressive tightening by making ground and supply trace areas as large as pos-
of regulations covering the amount of permissible radiated sible (Figure 3). This measure lowers the trace impedances.
system noise. This article presents empirical and analytical As a side benefit, it helps to conserve the etchant bath in the
techniques for effective EMI control of 54HC/74HC manufacturing process.
high-speed CMOS-logic circuitry.
Several sources conduct or radiate EMI from electronic ap- MEASURE PC-BOARD NOISE FOR EMI CONTROL
paratus. Among these are A simple but effective technique for isolating noisy circuit ar-
• antenna loops formed by ICs and their decoupling