SLUA887A August 2018 – September 2023 LM2005 , LM2101 , LM2103 , LM2104 , LM2105 , LM25101 , LM27222 , LM2724A , LM5100A , LM5100B , LM5100C , LM5101 , LM5101A , LM5101B , LM5101C , LM5102 , LM5104 , LM5105 , LM5106 , LM5107 , LM5108 , LM5109 , LM5109A , LM5109B , LM5109B-Q1 , LM5113-Q1 , LMG1205 , LMG1210 , SM72295 , SM74104 , TPS28225 , TPS28225-Q1 , TPS28226 , TPS2832 , TPS2836 , TPS2837 , UC2950 , UCC27200 , UCC27200-Q1 , UCC27200A , UCC27201 , UCC27201A , UCC27201A-DIE , UCC27201A-Q1 , UCC27211 , UCC27211A , UCC27211A-Q1 , UCC27212 , UCC27212A-Q1 , UCC27222 , UCC27282 , UCC27282-Q1 , UCC27284 , UCC27284-Q1 , UCC27288 , UCC27289 , UCC27301A , UCC27301A-Q1 , UCC27311A , UCC27311A-Q1 , UCC27710 , UCC27712 , UCC27712-Q1 , UCC27714
Driving MOSFETs in half-bridge configurations present many challenges for designers. One of those challenges is generating bias for the high-side FET. A bootstrap circuit takes care of this issue when properly designed.
This document uses UCC27710, TI's 620V half-bridge gate driver with interlock to present the different components in a bootstrap circuit and how to properly select them in order to ensure predictable switching of the power FETs.
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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.
