An Advanced Bootstrap Circuit for High Frequency, High Area-Efficiency and Low EMI Buck Converter

摘要

An advanced bootstrap control circuit with directly sensing bootstrap voltage (DSBV) for a high frequency, high area-efficiency, and low electromagnetic interference (EMI) buck converter in automotive applications is proposed in this brief. By removing the large off-chip capacitor at the output V-CC of low-dropout regulator (LDO), the relevant current loop around V-CC to power ground can be eliminated, which is a great contribution for EMI noise mitigation. On the other hand, the fast charging control for bootstrap capacitance has been substituted by a novel bootstrap architecture and is not dependent on the internal capless LDO, which will not degrade high-frequency behavior for the high-side gate driver. This buck converter has been implemented in a 0.35 mu m high-voltage BCD process and occupies a chip area of 2x2.39 mm(2), where the active area of bootstrap circuit is 320x194 mu m(2). Experimental results show that the bootstrap capacitance can be fully charged at MHz switching frequency with a small quiescent current of 43 mu A.