Synchronous buck-boost controller for wide-input-rail designs
The Texas Instruments LM5176RHFT is a synchronous buck-boost switching regulator controller that regulates a positive output voltage from an input that can be above, below, or equal to the output. Its 4.2 V to 55 V supply range covers 12 V and 24 V industrial buses, automotive battery rails through cold-crank and load-dump, and multi-cell Li-ion battery packs without a cascaded pre-regulator. The controller drives an external transistor pair in a single-inductor, four-switch buck-boost topology with synchronous rectification, which maintains efficiency when the input voltage crosses the output regulation point. Switching frequency is programmable from 100 kHz to 600 kHz and includes a clock sync input for system-level EMI management. Control features on the 28-VFQFN (5x4 mm) package include current limit, enable, frequency control, power-good flag, and a programmable soft start. The junction temperature range of -40°C to 125°C qualifies it for under-hood automotive, outdoor telecom, and industrial motor-drive environments.
Wide input range — what the 4.2 V to 55 V supply means for your rail budget
The 4.2 V minimum supply means this part regulates through the bottom of a 5 V rail during brownout and can run directly from a 4-cell Li-ion battery near its discharge floor. The 55 V maximum covers 24 V industrial rails with 20% tolerance plus transient spikes, and handles automotive 12 V system load-dump events without an external clamp. A buck-boost topology is the right choice when the input can swing both below and above the target output — a simple buck or boost alone would lose regulation at one end of the range.
Active production — no LTB risk on this BOM line
The LM5176RHFT carries an Active product status, meaning Texas Instruments continues to manufacture and support the part for new designs. There is no last-time-buy window to track, no NRND flag, and no forced redesign horizon for the production BOM. The part is ROHS3 compliant per the current revision.
Package and thermal — 28-VFQFN with exposed pad
The 28-VFQFN Exposed Pad package (5x4 mm body) requires a thermal via array under the pad to conduct heat into the PCB ground plane. Without that stitch, junction temperature rises quickly when the external MOSFETs switch at high duty cycles. The package is surface-mount only, supplied in Tape & Reel or Cut Tape options.