SNVAA61 February   2023 LM5168 , LM5168-Q1 , LM5169 , LM5169-Q1

 

  1.   Inverting Buck-Boost Application for LM5168
  2.   Trademarks
  3. 1Inverting Buck-Boost Topology
    1. 1.1 Concept
    2. 1.2 Output Current Calculations
    3. 1.3 Voltage Range of Inverting Buck-Boost Configuration
  4. 2Design Considerations
    1. 2.1 Bypass Capacitor and Optional Schottky Diode
  5. 3External Components
    1. 3.1 Capacitor Selection
    2. 3.2 Inductor Selection
  6. 4Digital Pin Configurations
    1. 4.1 Optional Enable (EN) Level Shifter
    2. 4.2 Power-Good (PG) Pin
  7. 5Typical Performance
    1. 5.1 VOUT = -12 V Typical Performance
    2. 5.2 VOUT = -24 V Typical Performance
    3. 5.3 VOUT = -48 V Typical Performance
  8. 6Conclusion
  9. 7References

6 Conclusion

The LM5168 is a buck converter that can be configured as an inverting buck-boost (IBB) topology by changing the output voltage and ground connections. Since the IBB is referenced to -VOUT rather than ground, the input voltage range of the LM5168 is limited depending on the magnitude of -VOUT. The maximum possible output current is also limited since the maximum inductor current is always larger than the maximum output current. This report explains the IBB topology and how to select the external components for a design. Data is provided from a test circuit. For further reading on the inverting buck-boost topology, refer to the Working with Inverting Buck-Boost Converters application note.