SLVA478C October   2013  – November 2022 TPS62120 , TPS62122

 

  1.   Using the TPS62120 in an Inverting Buck-Boost Topology
  2.   Trademarks
  3. 1Inverting Buck-Boost Topology
    1. 1.1 Design Considerations
    2. 1.2 Concept
    3. 1.3 Output Current Calculations
    4. 1.4 VIN and VOUT Range
  4. 2Digital Pin Configurations
    1. 2.1 Enable Pin
    2. 2.2 SGND Pin
    3. 2.3 Power Good Pin
  5. 3Startup Behavior and Switching Node Consideration
  6. 4External Component Selection
    1. 4.1 Inductor Selection
    2. 4.2 Input Capacitor Selection
    3. 4.3 Selecting L and COUT for Stability
  7. 5Typical Performance and Waveforms
  8. 6Conclusion
  9. 7References
  10. 8Revision History

1.4 VIN and VOUT Range

The input voltage that can be applied to an inverting buck boost converter IC is less than the input voltage that can be applied to the same buck converter IC. This is because the ground pin of the IC is connected to the (negative) output voltage. Therefore, the input voltage across the device is VIN to VOUT, not VIN to ground. Thus, the input voltage range of the TPS62120 is 2 V to 15 + VOUT, where VOUT is a negative value.

The output voltage range is the same as when configured as a buck converter, but negative. The output voltage for the inverting buck boost topology should be set between –1.2 V and –5.5 V. It is set the same way as in the buck configuration, with two resistors connected to the FB pin.