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

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 ${V} _{\text {CC}}$ of low-dropout regulator (LDO), the relevant current loop around ${V} _{\text {CC}}$ 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 }\text{m}$ high-voltage BCD process and occupies a chip area of $2 {\times }2.39$ mm ² , where the active area of bootstrap circuit is $320 {\times } 194\,\, {\mu }\text{m}^{{2}}$ . Experimental results show that the bootstrap capacitance can be fully charged at MHz switching frequency with a small quiescent current of 43 $ {\mu }\text{A}$ .