SNVA941A June   2020  – November 2022 LM5156 , LM5156-Q1 , LM51561 , LM51561-Q1 , LM51561H , LM51561H-Q1 , LM5156H , LM5156H-Q1

 

  1.   How to Design a Boost Converter Using the LM5156
  2. 1LM5156 Design Example
  3. 2Example Application
  4. 3Calculations and Component Selection
    1. 3.1  Switching Frequency
    2. 3.2  Inductor Calculation
    3. 3.3  Current Sense Resistor Calculation
      1. 3.3.1 Current Sense Resistor and Slope Compensation Resistor Selection
      2. 3.3.2 Current Sense Resistor Filter Calculation
    4. 3.4  Inductor Selection
    5. 3.5  Diode Selection
    6. 3.6  MOSFET Selection
    7. 3.7  Output Capacitor Selection
    8. 3.8  Input Capacitor Selection
    9. 3.9  UVLO Resistor Selection
    10. 3.10 Soft-Start Capacitor Selection.
    11. 3.11 Feedback Resistor Selection
    12. 3.12 Control Loop Compensation
      1. 3.12.1 Select the Loop Crossover Frequency (fCROSS)
      2. 3.12.2 Determine Required RCOMP
      3. 3.12.3 Determine Required CCOMP
      4. 3.12.4 Determine Required CHF
    13. 3.13 Efficiency Estimation
  5. 4Component Selection Summary
    1.     25
  6. 5Small-Signal Frequency Analysis
    1. 5.1 Boost Regulator Modulator Modeling
    2. 5.2 Compensation Modeling
    3. 5.3 Open-Loop Modeling
  7. 6Revision History

3.9 UVLO Resistor Selection

The external under voltage lockout (UVLO) resistors set the minimum operating voltage of the regulator. Two levels must be specified; the voltage the LM5156 device starts operation (VSUPPLY(ON)) and the voltage the LM5156 enters stand-by mode (VSUPPLY(OFF)). In this example, VSUPPLY(ON) voltage is 2.6 V and the VSUPPLY(OFF) is 2.2 V. Using Equation 19, the top UVLO resistor (RUVLOT) is calculated.

Equation 19. GUID-1DA851CF-6761-4792-AD71-5784F3D3478B-low.gif

A standard value of 60.4 kΩ is selected for RUVLOT. Using Equation 20 the top UVLO resistor (RUVLOB) is calculated

Equation 20. GUID-61345D0E-A9B7-453B-BEB7-C6FCEE43CDEB-low.gif

A standard value of 80.6 kΩ is selected for RUVLOB