SLVAF45 August   2021 TPS51397A , TPS566231 , TPS566235 , TPS566238 , TPS568230

 

  1.   Trademarks
  2. 1Introduction
  3. 2Why We Need Cff in High Output Voltage D-CAP2/3 Converter for Stability
  4. 3Effects of Feedforward Capacitor on the Loop
  5. 4Cff Choose Method
  6. 5Application Design Example of D-CAP2/D-CAP3 Converter with Cff
  7. 6Experimental Verification
  8. 7Conclusion
  9. 8References
  10. 9Appendix A

9 Appendix A

For TPS568230 Ioutmax=8 A, Vref=0.6 V. Co in the table are effective value considering degrading. The large Cff as 1000 pF can be allowed from loop stability view, but it could inject more high frequency noise into feedback and also might affect converter operation. The Cff theoretical calculation methods must be used combined with real situation and bench test results.

Table 9-1 Validation Results for the Proposed Method
Vin (V) Vo (V) fsw (kHz) Rtop/Rbottom Llimits (uH) Lchoose(uH) Co (uF) Cff limit Cff choose (pF) PMtest (deg)
6 2.5 600 95 kΩ/30 kΩ 0.76-1.52 1 200 Cff>56pF 70 81.4
1000 50.8
6 3.3 600 90 kΩ/20 kΩ 0.77-1.55 1 200 Cff>68 pF 80 80.2
1000 47
18 2.5 600 95 kΩ/30 kΩ 1.12-2.24 1.5 200 Cff>69 pF 82 80
1000 63
18 3.3 600 90 kΩ/20 kΩ 1.4-2.81 2.2 200 100-236 pF 110 83
220 75
18 5 600 220 kΩ/30 kΩ 1.88-3.76 2.2 200 51-147 pF 62 72
140 77