Microchip Technology ADM00732, Руководство пользователя

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HV7358DB1 User’s Guide
DS50002951A-page 48
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2020 Microchip Technology Inc.
5.1.4 Decoupling Capacitors
The PCB layout decoupling capacitor’s placement rule is simple: place the capacitor as
close as possible to the pin being decoupled. The actual placement of the capacitor
may generate EMI/RFI. The placement determines the return current path. The return
path is from the GND side of the bypass cap, through the PCB trace, through any vias,
through the GND plane and back to the GND pin on the HV7358.This path also needs
to be as short as possible. There are also high current spikes from the VPP and VNN
supplies to the HV7358 TX outputs. Use the same design rules with TX output traces
and vias.
5.1.5 Return Current Design in PCB Layout
Many EMI problems associated with the high-speed circuits are due to improper design
of the return current path. PCB designers put considerable effort into carefully
designing traces with the proper length, proper transmission line impedance, etc., but
neglect the return current path that completes the current loop
. These EMI problems
can usually be avoided with proper design of the return current path.