SLUAAJ0 February   2024 TPS51397A , TPS54308 , TPS54320 , TPS54350 , TPS54620 , TPS54622 , TPS54821 , TPS54824 , TPS563300 , TPS566231 , TPS566235 , TPS566238 , TPS568230 , TPS56C215 , TPS62933 , TPS62933F , TPS62933O

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Comparison of Feedback Sense Methods with Second Stage Filter
  6. 3Transfer Function Derivation of PCM Converter with Second Stage Filter and Hybrid Sense
  7. 4Overall Loop Model
  8. 5Zero and Pole Analysis
  9. 6Stability Design Method
  10. 7Design Example and Experimental Validation with TPS62933F
  11. 8Summary
  12. 9References
  13.   A Appendix

Abstract

In power design for applications such as ADC, RF transceiver and analog front end (AFE), output voltage ripple is an important factor for power quality evaluation. In previous DC-DC power supply, two-stage power design, including buck converter and LDO, are normally used to support low output voltage ripple requirement. In recent years, a type of power design using buck converter and secondary stage passive filter attracts more attention. Compared with conventional design with LDO, reduced design size and total efficiency improvement can be achieved. But a pair of conjugate poles can be introduced by the added passive filter, which threatens the loop stability.

In Peak Current Mode Converter Secondary Stage Filter Design for Low Ripple Power – Part I: Filter Design for Output Ripple Reduction application note, the second stage filter components selection method to achieve required output voltage ripple is introduced. In Part II, the hybrid sense network design method for stability is further studied. The loop response of peak current mode converter with second stage filter is analyzed at first. On the basis, the stability design method is proposed. Finally, an application design flow is proposed and it is verified by experiments with TPS62933F.