A 4-to-42-V Input 3.3-V Output Self-Biased DC–DC Buck Converter Featuring Leakage-Emulated Bootstrap Voltage Refresher and Anti-Deadlock

This letter presents a 4-to-42-V input and 3.3-V output dc–dc buck converter for battery-powered automotive uses. Pulse-frequency modulation (PFM) is a common scheme employed to reduce quiescent current $(I_{Q})$ and mitigate battery drain. However, sustaining the bootstrap voltage $(V_{B})$ , essential for activating power switches, becomes arduous at elevated temperatures due to significant leakage currents, particularly when the switching frequency is low in no-load scenarios. To address this issue, this letter proposes a leakage-emulating oscillator-based (LEOB) refresher that stabilizes $V_{B}$ , even at temperatures as high as +125 °C. Additionally, an anti-deadlock self-bias supply is presented to further reduce $I_{Q}$ while ensuring fault tolerance. The chip, fabricated in a 180-nm BCD process, exhibits a low $I_{Q}$ of 3.2 $\mu \text{A}$ and a peak efficiency of 95.5% (93.3%) at $V_{\mathrm{ IN}}\,\,=$ 24 V (42 V), with demonstrated stability of $V_{B}$ from −40 °C to +125 °C.