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

2.3.1 Using Net Ties to Separate Routing

GUID-20230210-SS0I-GCZ3-FRL5-NKKPV9RSXQ5V-low.svg Figure 2-3 Example of Using the Net-Tie to Treat CSA and SW1 as Separate Nodes

In some cases, the designer does recognize the need of two separate nodes. But during the finishing of the board, the layout treats the CSA and SW1 as same nets. This unintended connection can happen anywhere along the trace. A net tie allows an artificial separation of net names in the schematic as shown in Figure 2-3. This allows the layout tool to treat CSA and SW1 as separate nodes and protects the differential trace (CSA) from accidental connections . The pins CSA and SW1 are marked as shown in Figure 2-3. Net ties act like a zero-ohm resistor and allow to define the connection point of the two nets on the PCB.