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.