Four-rail power manager for space-constrained boards
The TPS65400RGZR is a four-output step-down (buck) regulator from TI, packing two 4 A rails and one 2 A rail into a single 48-VFQFN exposed-pad package. That fourth output? A low-current auxiliary rail for sequencing or housekeeping. The adjustable output (0.6 V to 16.2 V) and synchronous rectifier keep the BOM lean — no external Schottky catch diode needed. Input range spans 4.5 V to 18 V, so it handles 5 V, 9 V, 12 V, and 15 V buses without a pre-regulator. The 48-VQFN (7x7 mm) footprint with exposed pad demands a good thermal via pattern under the paddle — the 125 °C junction rating is real, but the board copper carries the heat.
Switching frequency: trade inductor size for efficiency
The programmable switching frequency from 275 kHz to 2.2 MHz lets you optimise the power stage. Run at 275 kHz for best efficiency and lower switching losses; push toward 2.2 MHz to shrink the inductor footprint, at the cost of higher gate-drive losses and tighter layout requirements. The 48-VQFN package's exposed paddle helps pull heat from the high-frequency FETs.
TI lists the TPS65400RGZR as Active. No official pin-compatible alternate is listed, so dual-sourcing would require a layout change.