SLYA094 August   2025 LM5137F-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Hardware Design with LM5137F-Q1
    1. 2.1 Schematic
  6. 3PMP41158 Performance Curves
    1. 3.1 Four-Phase Interleaving
    2. 3.2 Thermal Performance
    3. 3.3 Load Transient
    4. 3.4 Light Load Efficiency
    5. 3.5 Bode Plot
  7. 4Reference Design Modification Conversion From 48V to 12V
  8. 5Summary
  9. 6References

3.3 Load Transient

To achieve high slew rates of 62A/us for the load transient test, the reference design requires an onboard load stepper circuit, as Figure 3-4 shows. In theory, the MOSFET used in the load stepper works in linear region which is controlled by the gate to source voltage, VGS. By modulating the gate to source voltage, we adjust the current slew rate of the load step. The onboard load stepper is capable of achieving up to 100A/us load step slew rate.

Onboard Load Stepper CircuitFigure 3-4 Onboard Load Stepper Circuit
Load Transient Test Figure 3-5 Load Transient Test

For load stepper set up details, please refer to PMP41158: 450W Four-Phase Interleaved Buck Converter Reference Design.

Note: Since different MOSFET has the different gate charge specifications, using different MOSFET can result in the need to tune the VGS voltage to attain the required load step slew rate.