WR0309-AT

WR0309-AT is a SOT-89-3 LDO, 2.5/3.3/5.0, up to 0.3. Pin-compatible families include LM1117 / NCP1117 / LD1117 (same SOT-223 or TO-252 footprint). Match dropout voltage and the output-capacitor ESR rule before swapping.

Use an LDO for low-current, noise-sensitive rails (analog / RF, small ΔV). Use a DC-DC (buck) when the input-output voltage gap is large or efficiency / battery life matters. A common hybrid: DC-DC first, then LDO to clean the rail.

Legacy 1117-class LDOs need output-cap ESR between 0.3 Ω and 22 Ω; all-ceramic caps (very low ESR) can oscillate — add a 1–3 Ω series resistor or a small electrolytic. Modern LDOs are stable with low-ESR MLCCs.

Buy only from authorized or franchised channels. On receipt, check: (1) laser-etched markings that solvent will not remove; (2) batch / lot code consistent between label and device; (3) original reel or tube packaging; (4) request traceability documents (CoC, date code). For critical parts, third-party X-ray / decapsulation testing is recommended.

Most active ICs use a 4-digit date code YYWW (year + week, e.g. 2345 = 2023 week 45). The top mark is manufacturer logo + base part number + lot code. For SMD code lookup, search by "marking code + package" on AllDataSheet / Octopart / LCSC.

Package codes describe the physical form factor and pin layout — critical when sourcing, because electrically equivalent parts in different packages will not fit the PCB. Common: TO-220 (3-terminal power), SOT-23 (3-pin small signal), DIP / SOIC (through-hole / SMD ICs), QFP / QFN (MCUs, processors).

Three options: (1) the manufacturer’s recommended replacement; (2) franchised distributor legacy stock; (3) a functionally compatible cross-brand part — provided pinout and key parameters match. Always evaluate on a real board before mass swap.

We support both sample and volume orders. Minimum order quantity, stock availability and lead time are confirmed per inquiry — tell us your model and quantity and we will quote. Sample quantities for design validation are supported.

The full datasheet is linked on this page. For parts without a direct datasheet, we can locate the manufacturer document on request. Sample requests are supported — contact us with your model and quantity.