SNVAA43 March   2023 LM5157 , LM5157-Q1 , LM51571-Q1 , LM5158 , LM5158-Q1 , LM51581 , LM51581-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Application Parameters
  5. 3Calculations and Component Selection
    1. 3.1 Switching Frequency
    2. 3.2 Coupled Inductor Selection
      1. 3.2.1 Coupling Capacitor (AC Cap)
    3. 3.3 Diode Selection
    4. 3.4 MOSFET Selection
    5. 3.5 Output Capacitor Selection
    6. 3.6 Input Capacitor Selection
    7. 3.7 Output Voltage Setting
  6. 4Simplified SEPIC Schematic
  7. 5References

2 Application Parameters

The following parameters are needed to calculate the SEPIC power stage:

  • Input voltage range
  • Nominal output voltage
  • Maximum output current
  • Maximum output power
  • Desired switching frequency
  • Converter IC

Table 2-1 shows the specification for the example application.

Table 2-1 Application Specification
Parameter
VIN4 V to 32 V
VLOAD12 V
ILOAD1 A
POUT, max12 W
fSW2.1 MHz