SLVAFU9 January   2025 TPS62840 , TPS62843

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Inverting Buck-Boost Topology
    1. 1.1 Concept
    2. 1.2 Output Current Calculations
    3. 1.3 VIN and VOUT Range
  5. 2Design Considerations
    1. 2.1 Additional Input Capacitor
    2. 2.2 Digital Input Pin Configurations
    3. 2.3 Startup Behavior and Switching Node Consideration
  6. 3External Component Selection
    1. 3.1 Inductor Selection
    2. 3.2 Capacitor Selection
  7. 4Typical Performance
  8. 5Summary
  9. 6References

3.1 Inductor Selection

To select the inductor value for the inverting buck-boost topology, use Equation 1 through Equation 4 instead of the equations provided in the TPS62840 data sheet. These formulas help to select the proper inductance by designing for a maximum inductor current (IL(Max)) or finding the peak inductor current for a given inductance. IL(Max) needs to be kept below the device minimum current limit value for a reliable design. The worst-case IL(Max) occurs at the minimum VIN for a given design. Once IL(Max) is determined, the recommendation is to choose an inductor with a saturation rating 20 % to 30 % higher than IL(Max) to allow for peak currents that can occur during startup or load transients. For the inverting buckboost topology, the recommended inductance is 2.2μH.