SLVA469D June   2013  – January 2023 TLV62130 , TLV62130A , TLV62150 , TLV62150A , TPS61175 , TPS61175-Q1 , TPS62130 , TPS62130A , TPS62131 , TPS62132 , TPS62133 , TPS62135 , TPS62136 , TPS62140 , TPS62140A , TPS62141 , TPS62142 , TPS62143 , TPS62150 , TPS62150A , TPS62151 , TPS62152 , TPS62153 , TPS62160 , TPS62161 , TPS62162 , TPS62163 , TPS62170 , TPS62171 , TPS62172 , TPS62173

 

  1.   Using the TPS6215x in an Inverting Buck-Boost Topology
  2.   Trademarks
  3. 1Inverting Buck-Boost Topology
    1. 1.1 Concept
    2. 1.2 Output Current Calculations
    3. 1.3 VIN and VOUT Range
  4. 2Design Considerations
    1. 2.1 Design Precautions
    2. 2.2 Additional Input Capacitor
    3. 2.3 Digital Pin Configurations
      1. 2.3.1 Digital Input Pins (EN, FSW, DEF)
      2. 2.3.2 Power Good Pin
    4. 2.4 Startup Behavior and Switching Node Consideration
  5. 3External Component Selection
    1. 3.1 Inductor Selection
    2. 3.2 Capacitor Selection
  6. 4Typical Performance
  7. 5Conclusion
  8. 6References
  9. 7Revision History

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 TPS62150 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) should 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, it is recommended to choose an inductor with a saturation rating 20% to 30% higher than IL(Max) to allow for peak currents that may occur during startup or load transients. For the inverting buck-boost topology, the minimum recommended inductance is 2.2 μH. If more efficient, half-frequency operation is desired (FSW = high), then a 3.3-μH inductor is the recommended minimum value. The FSW pin should be connected to ground to set it to a logic high.