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Bootstrap circuit with high-voltage charge storing for area efficient gate drivers in power management systems

  • Bootstrap circuits are mainly used for supplying a gate driver circuit to provide the gate overdrive voltage for a high-side NMOS transistor. The required charge has to be provided by a bootstrap capacitor which is often too large for integration if an acceptable voltage dip at the capacitor has to be guaranteed. Three options of an area efficient bootstrap circuit for a high side driver with an output stage of two NMOS transistors are proposed. The key idea is that the main bootstrap capacitor is supported by a second bootstrap capacitor, which is charged to a higher voltage and connected when the gate driver turns on. A high voltage swing at the second capacitor leads to a high charge allocation. Both bootstrap capacitors require up to 70% less area compared to a conventional bootstrap circuit. This enables compact power management systems with fewer discrete components and smaller die size. A calculation guideline for optimum bootstrap capacitor sizing is given. The circuit was manufactured in a 180nm high-voltage BiCMOS technology as part of a high-voltage gate driver. Measurements confirm the benefit of high-voltage charge storing. The fully integrated bootstrap circuit including two stacked 75.8pF and 18.9pF capacitors results in a voltage dip lower than 1V. This matches well with the theory of the calculation guideline.

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Author of HS ReutlingenSeidel, Achim; Wicht, Bernhard
Erschienen in:ESSCIRC 2014 - 40th European Solid State Circuits Conference : Venice, Italy, 22 - 26 September 2014
Place of publication:Piscataway, NJ
Editor:Pietro Andreani, Andrea Bevilacqua, Gaudenzio Meneghesso
Document Type:Conference proceeding
Publication year:2014
Tag:bootstrap circuits; driver circuits
Page Number:4
First Page:159
Last Page:162
DDC classes:621 Angewandte Physik
Open access?:Nein
Licence (German):License Logo  In Copyright - Urheberrechtlich geschützt