SLVAE69 July   2019 TPS568215 , TPS56C215


  1.   Expand Buck Converter Minimum Input Voltage with External VCC Bias
    1.     Trademarks
    2. 1 TPS56C215 Introduction
    3. 2 12 V / 5 V O-ring supply for DDR application
    4. 3 Schematic and Bench Results
      1. 3.1 Efficiency Comparison
      2. 3.2 Bench Waveforms
    5. 4 Conclusion
    6. 5 References

Expand Buck Converter Minimum Input Voltage with External VCC Bias

A typical step down (buck) converter has an internal linear low-drop-out (LDO) power supply for internal logic control and circuit drive capability. Integrating the output pin and capacitor of the LDO can help save IC pin count as well as reduce solution size; however, taking the approach of utilizing an external bias cap can provide stronger capability to drive the circuit. Additionally, using an external VCC bias allows the use of a device in lower input voltage applications while also increasing efficiency.

TPS56C215 is a monolithic 12-A synchronous buck converter with an adaptive on-time D-CAP3™ control mode. Using TPS56C215 as an example, this application note introduces a method of using an external VCC bias to support lower input voltage (VIN) applications. First, this report will describe the features of the TPS56C215 device before an example of a low input voltage application is introduced. Then, a detailed schematic with the external VCC bias configuration is presented, followed by the confirmation of this theory via bench testing and an efficiency comparison.