SLVAFW0 December   2025 TPS61381-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2TPS61381-Q1 Schematic Guideline
    1. 2.1 GND Connection
    2. 2.2 Driver Design
    3. 2.3 IO Configuration
    4. 2.4 Output Capacitor
    5. 2.5 Compensation Design
      1. 2.5.1 Small Signal Analysis
      2. 2.5.2 Step by Step Loop Compensation Design
  6. 3TPS61381-Q1 Layout Guide Line
    1. 3.1 Identification of the Critical Switching Loops
      1. 3.1.1 Low Side Driver Loop
      2. 3.1.2 Boost Leg Switching Loop
      3. 3.1.3 High Side Driver Loop
    2. 3.2 Power Component Placement
    3. 3.3 Layout Example
      1. 3.3.1 Optimizing Low Side Driver Loop Example
      2. 3.3.2 Optimizing Boost Leg Switching Loop Example
      3. 3.3.3 Optimizing High Side Driver Loop Example
      4. 3.3.4 Signal Circuit Routing Example
  7. 4Summary
  8. 5References

3.1.1 Low Side Driver Loop

Driver loop is one of the most critical loops for all switching regulators. When the IC turns on the MOSFET, current flows from the VCC capacitor through internal driver and gate resistor to charge the gate capacitance of low side MOSFET. The return current flow from the source of low side MOSFET(PGND), through net-tie to and return to VCC capacitor(AGND). When the IC turns off the MOSFET, gate capacitance of low side MOSFET is discharged. Current flows from the MOSFET gate through gate resistor into the LO pin, and eventually to the AGND pin. The return current flow from the IC AGND pin, through net-tie to and return to MOSFET gate capacitance (PGND). These charge and discharge current is generated within several ns and the peak current can reach up to 2A. So parasitic inductance in this current loop can create ringing on MOSFET gate and thus affect the effectiveness of the driver. Switching ringing can even cause boost leg shooting through and damage the device if the layout is not carefully designed. Low side driver current path is depicted in Figure 3-1.

TPS61381-Q1 Low Side Driver Current Path Figure 3-1 TPS61381-Q1 Low Side Driver Current Path