TIDUET3 February   2021

 

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4.1.3 PCB Layout Recommendations

The key guidelines for routing power stage components follows:

  • Minimize the loop area and trace length of the power path circuits, which contain high-frequency switching currents, on both the primary and secondary sides of the converter. This helps reduce EMI and improve converter overall performance.
  • Keep traces with high dV/dt potential and high dI/dt capability away from or shielded from sensitive signals.
  • Keep power ground and control ground separated for each power supply stage. If they are electrically connected, tie them together at one point near the DC input return or output return of the given stage correspondingly.
  • When multiple capacitors are used in parallel for current sharing, the layout must be symmetrical across both leads of the capacitors. If the layout is not identical, the capacitor with the lower series trace impedance will see higher currents and become hotter.
  • Place protection devices such as TVS, snubbers, capacitors, or diodes physically close to the device. Devices are intended for protection and hence must be routed with short traces to reduce inductance.
  • Choose the width of PCB traces based on acceptable temperature rise at the rated current per IPC2152 as well as acceptable DC and AC impedances. Also, the traces must withstand the fault currents (such as short-circuit current) before the activation of electronic protection such as a fuse or circuit breaker.
  • Determine the distances between various circuits according to the requirements of applicable standards such as the UL60950.
  • Adapt thermal management to fit the end-equipment requirements.