SLUA887A August   2018  – September 2023 UCC27201A , UCC27710 , UCC27712 , UCC27714

 

  1.   1
  2.   Bootstrap Circuitry Selection for Half-Bridge Configurations
  3.   Trademarks
  4. 1Introduction
  5. 2Basic Operation of Bootstrap Circuit
  6. 3Bootstrap Components Selection
    1. 3.1 Bootstrap Capacitor
    2.     8
    3. 3.2 VDD Bypass Capacitor
    4. 3.3 External Bootstrap Diode
    5.     11
    6. 3.4 Bootstrap Resistor
    7.     13
  7. 4Layout Considerations for Bootstrap Components
  8. 5Summary
  9. 6References
  10. 7Revision History

1 Introduction

When using half-bridge configurations, it is necessary to generate high-side bias to drive the gate of the high-side FET referenced to the switch node. One of the most popular and cost effective way for designers to do so is the use of a bootstrap circuit which consists of a capacitor, a diode, a resistor and a bypass capacitor.

This application report will explain how this circuit works, the key components of the bootstrap circuits and their impact in the gate drive. This app note will put emphasis on half-bridge gate drives using drivers with no built-in bootstrap diode, which gives designers flexibility and reduces power dissipation in the gate driver IC. Additionally, it will discuss the layout considerations for the different components of this circuit.