SNVA940 November   2021 LM5157 , LM5157-Q1 , LM51571-Q1 , LM5158 , LM5158-Q1 , LM51581 , LM51581-Q1

 

  1.   Trademarks
  2. 1LM5157 Boost Design Example
  3. 2Calculations and Component Selection
    1. 2.1  Switching Frequency
    2. 2.2  Inductor Calculation
    3. 2.3  Slope Compensation Check
    4. 2.4  Inductor Selection
    5. 2.5  Diode Selection
    6. 2.6  Output Capacitor Selection
    7. 2.7  Input Capacitor Selection
    8. 2.8  UVLO Resistor Selection
    9. 2.9  Soft-Start Capacitor Selection
    10. 2.10 Feedback Resistor Selection
    11. 2.11 Control Loop Compensation
      1. 2.11.1 Crossover Frequency (fcross) Selection
      2. 2.11.2 RCOMP Selection
      3. 2.11.3 CCOMP Selection
      4. 2.11.4 CHF Selection
    12. 2.12 Power Loss and Efficiency Estimation
  4. 3Implementation Results
  5. 4Small Signal Frequency Analysis
    1. 4.1 Boost Regulator Modulator Modeling
    2. 4.2 Compensation Modeling
    3. 4.3 Open Loop Modeling

Compensation Modeling

Table 4-2 includes equations model a type II compensation network implemented using a transconductance error amplifier.

Table 4-2 Compensation Modeling Equations
Simplified Formula Comprehensive Formula
Feedback Equations
Feedback Transfer Function
Equation 50. GUID-DFC2D9D8-1EF4-41A4-A660-48CA19AB4F73-low.gif
Feedback DC Gain
Equation 51. GUID-82E26F47-6CAB-45E7-8F38-44FDB2F1B7D2-low.gif
Equation 52. GUID-A2ED2ECF-04BE-4457-8E93-5BBDE9BD27B2-low.gif
Low Frequency Zero
Equation 53. GUID-2E7795A9-97D2-47BC-BADB-9FBF3569115F-low.gif
Equation 54. GUID-70C73007-3C5B-4BC0-8837-66846A2A394B-low.gif
High Frequency Pole
Equation 55. GUID-2B4B9492-227F-44A0-AD2C-3C2332062B9D-low.gif
Equation 56. GUID-3BB54BAA-87CC-44E2-A0B5-514C6E537598-low.gif
Mid-band Gain
Equation 57. GUID-2B0AAF18-AE35-46B3-9D92-4E9383450126-low.gif
Equation 58. GUID-DC49433C-B489-460B-9A01-03F082EB1A1C-low.gif
  1. gm is the transconductance of the error amplifier, 2mA/V