What this part does and where it goes
The Texas Instruments UCC25800AQDGNRQ1 is an open-loop LLC transformer driver designed for isolated power transfer in automotive systems. It integrates the switching stage for a resonant LLC half-bridge topology, delivering a regulated output through a transformer without requiring a feedback loop on the secondary side. The part is AEC-Q100 qualified and operates from a 9V to 34V supply, making it suitable for 12V and 24V vehicle electrical systems, as well as industrial battery-backed rails. Typical applications include isolated gate-drive bias supplies, auxiliary power for traction inverters, and on-board charger housekeeping rails where galvanic isolation is needed.
The 9V to 34V input range covers both nominal 12V and 24V automotive buses, including cold-crank and load-dump transients within the abs-max window. The 14mA supply current is the driver's own consumption at no load — budget additional current for the transformer primary and any secondary load when sizing the upstream rail. The open-loop LLC architecture means the switching frequency is set by external resistors and the transformer's resonant tank — no secondary-side regulation loop, which simplifies the design but requires careful transformer selection for load regulation.
Package and mounting
The UCC25800AQDGNRQ1 is supplied in an 8-HVSSOP package (also referred to as 8-PowerTSSOP) with an exposed thermal pad. The surface-mount footprint is compact — 3.00 mm body width — which suits space-constrained automotive ECU layouts.