40V 4-switch synchronous buck-boost — the wide-input workhorse
The Renesas ISL81401FRZ is a 40V, 4-switch synchronous buck-boost PWM controller designed for applications that need a regulated output from an input that swings above or below the target rail. Its 4.5V to 40V supply range covers automotive cold-crank through load-dump, industrial 24V bus with transients, and multi-cell battery packs. The 90kHz to 650kHz programmable switching frequency lets you optimise the inductor size against efficiency — lower frequency for best efficiency in a larger footprint, higher frequency to shrink the magnetics for dense boards. Synchronous rectification is built in, which keeps the efficiency curve competitive across light and heavy loads without external Schottky diodes.
No commercial-grade derating needed — the silicon is characterised and guaranteed over the full industrial span.
Control features and sourcing fit
The ISL81401FRZ integrates current limit, enable, and power-good monitoring — the three control signals that let a system controller sequence the rail, flag a fault, and shut down cleanly. The single output with positive configuration and two output phases means it drives a single regulated rail with interleaved phases for reduced ripple and smaller output capacitance.