SLVAFJ3 september   2023 LM5177 , LM51772

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Importance of DC-DC Power Supply Layout
  5. 2Steps for a Good Layout
    1. 2.1 Identifying Critical Circuit Paths
    2. 2.2 Optimizing Hot Loops in the Power Stage
    3. 2.3 Separating Differential Sense Lines From Power Planes
      1. 2.3.1 Using Net Ties to Separate Routing
    4. 2.4 Routing Gate-Drive and Return Paths
    5. 2.5 Controller Layout
    6. 2.6 Separate AGND and PGND
    7. 2.7 Thermal Vias
  6. 3Tips for Layout Optimization
  7. 4Layout Example
  8. 5Summary
  9. 6References

2.5 Controller Layout

With the provision to locate the controller as close as possible to the power MOSFETs to minimize gate driver traces, the components related to the analog and feedback signals as well as current sensing are considered in the following:

  • Separate power and signal traces, and use a ground plane to provide noise shielding.
  • Place all sensitive analog traces and components related to COMP, FB, SLOPE, SS/ATRK, and RT away from high-voltage switching nodes such as the following to avoid mutual coupling:
    • SW1
    • SW2
    • HO1
    • HO2
    • LO1
    • LO2
    • HB1
    • HB2
  • Use an internal layer or layers as ground plane or planes. Pay particular attention to shielding the feedback (FB) trace from power traces and components.
  • Route the CSA and CSB and ISNSP and ISNSN traces as differential pairs to minimize noise pickup and use Kelvin connections to the applicable shunt resistor. Place the filter components of these sense signals close to the controller to minimize noise pickup after them.
  • Locate the upper and lower feedback resistors close to the FB pin, keeping the FB traces as short as possible. Route the trace from the upper feedback resistor or resistors to the output voltage sense point.