Best Guidelines for High Speed Design

In this tutorial we are going to learn about Best Guidelines for High Speed Design

Circuit Design Tips:

  • Use the minimum clock speeds possible for logic circuitry.
  • Select the slowest switching speed logic.
  • Select the logic with the greatest noise margin.
  • Select logic families with the lowest switching energy.
  •  Avoid the use of both high impedance inputs and outputs.
  • Decouple RF currents to the RF ground at inputs and outputs.
  • Protect both inputs and outputs from RF Interference.
  • Decouple any RF currents on the PCB at the I/O terminations, if possible.
  • Take care when using non-linear devices & semiconductors at inputs & outputs to avoid rectification of any RF signals.
  •  Employ simple inductor/capacitor/resistor networks where possible to decouple Radio Frequencies.
  • Always use short connection tracks to decoupling networks to avoid adding inductance & impedance.
  • Use ferrite beads to damp out parasitic oscillations.
  • Keep all signal levels as high as possible to overcome noise thresholds. Where possible match input & output impedances (for HF).
  • Terminate unused inputs on devices & unused inputs on module to GND if possible
  • PCB Design Tips:
  • Avoid slit apertures in PCB layout, particularly in GND planes or near current paths.
  • In high speed PCB, Area of high impedance give rise to high EMI, so use wide tracce for power lines on the trace sides.
  •  Make signal tracks stripline & include GND plane & PWR plane whenever possible.
  • Keep HF/RF tracks as short as possible & layout the High Frequency trace first.
  • On sensitive components & terminations, use guard ring & Ground fill wherever possible.
  • If we make guard ring around on the trace layers which can reduces emission out of the board and also, connects to Ground only at a single point and makes no other use of the guard ring.
  • When you have separate power planes, keep them over a common Ground to reduce system noise and power coupling.
  • The power plane conductivity should be high, so avoid localized concentrations of via & through hole pads (surface mount is preferred mounting method).
  • Track mitering (beveling of edges and corners) reduces field concentration.
  • If possible, try to route the traces run orthogonally between adjacent layers.
  • Don’t loop tracks, even between layers, as this forms a receiving or radiating.
  • Try to don’t leave any  floating conductor areas, as they act as EMI radiators; if possible connect to GND plane (often, these sections are placed for thermal dissipation, so polarity shouldn’t be a consideration, but verify with component data sheet).

 

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