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Design aspects for digital PCB modules tutorial

Modules

1. Practical digital design rules

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  • Choose an appropriate logic family for functionality purposes. Do not use high-speed components when another logic family with a slower edge rate is acceptable. Components with fast edge rates generates greater amounts of spectral bandwidth of RF energy than devices with a slightly slower edge rate. Manufacturers of components rarely specify the minimum edge rate only the maximum rise and fall time to guarantee functional performance. 
  • Minimize inductive trace lengths of components by not using sockets for through-hole devices.
  • Select logic components with power and ground pins located in the middle and not on the corners. This minimizes lead length inductance and ground loops created by decoupling capacitors.
  • When selecting a decoupling capacitor, take into consideration the point source of charge a logic device requires for functionality. This is in addition to the resonant frequency required for removal of high-frequency RF currents developed from the component switching all pins simultaneously under maximum capacitive load.
  • Take into consideration the lead length of radial and axial capacitors when selecting a capacitor for a particular self-resonant range of frequency.

1. Practical digital design rules

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