Fixed 4.5 V boost for tight analog rails
The TPS61258YFFT is a step-up regulator from Texas Instruments that delivers a fixed 4.5 V output — no external feedback divider needed, which saves two resistors and one feedback-node noise path. The internal switch is rated for 3.9 A, so the output can support loads up to roughly 2.5 A at 4.5 V from a 3.3 V input, depending on inductor selection and efficiency. The 3.5 MHz switching frequency allows the use of small 1 µH to 2.2 µH inductors and ceramic output capacitors, keeping the total solution footprint compact.
Input range and output capability
The input voltage range runs from 2.65 V up to 4.35 V, which covers two-cell alkaline, single-cell Li-ion, and 3.3 V regulated rails. With a 3.3 V input, the part can boost to 4.5 V and deliver over 2 A to the load — enough to power a small RF PA or a string of LEDs. The fixed 4.5 V output is a common rail for USB On-The-Go (OTG) power, sensor bias, and as a pre-regulator for a low-dropout linear regulator that needs headroom. Because the output is fixed, there is no way to adjust it upward or downward — confirm that 4.5 V matches your load before layout.
The 9-DSBGA package requires careful PCB layout — the 0.50 mm pitch and small pad size demand a 4-layer board for fan-out and adequate thermal relief.