What this buck-boost does on the board
The LTC3129EUD-1#PBF is a synchronous buck-boost regulator from Analog Devices, delivering a programmable output up to 200 mA from an input range of 1.92 V to 15 V. Its buck-boost topology means the output stays regulated whether the input is above, below, or equal to the output voltage — useful when the supply rail sags below the target (like a battery discharging) or surges above it. Switching at 1.2 MHz, the part uses a synchronous rectifier — the internal low-side FET replaces the external Schottky diode, which improves efficiency at light loads and shrinks the inductor footprint. The single output is positive and programmable from a 2.5 V minimum up to 15 V.
Housed in a 16-lead WFQFN with exposed pad (3 mm × 3 mm), the LTC3129EUD-1#PBF is surface-mount and requires a thermal land on the PCB to pull heat from the die. The exposed pad is the primary thermal path — the datasheet layout recommendation ties it to the ground plane with multiple vias. Supplied in a tube (the listed package format), the part is also available in tape-and-reel under alternate order codes.