SNVAA65 March   2023 LM63610-Q1 , LM63615-Q1 , LM63625-Q1 , LM63635-Q1

 

  1.   Abstract
  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
  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 = -3.3 V, 2.1 MHz Typical Performance
    2. 5.2 VOUT = -3.3 V, 400 kHz Typical Performance
    3. 5.3 VOUT = -5 V, 2.1 MHz Typical Performance
    4. 5.4 VOUT = -5 V, 400 kHz Typical Performance
  8. 6Conclusion
  9. 7References

3.1 Capacitor Selection

The capacitance values for CIO and the high frequency capacitor CIO_HF can follow the data sheet recommendations for input capacitance when using the LM63615-Q1 as a buck converter. When using the LM63615-Q1, it is important to include a 220-nF high frequency ceramic capacitor, per data sheet recommendations, as part of the bypass capacitance that is connected as closely to the input of the regulator as possible. An additional CIN capacitance can be added to the inverting buck-boost as necessary. If needed, CIO and CIN can be increased. The output capacitance can also follow buck converter data sheet recommendations, but might need to be increased to improve performance.