PNDS / Marking codes / ST

Identify an unknown SMD part: marking code “ST”

Packages rarely print the full part number. The marking below is shared by several part numbers — use the package, pin count and the manufacturer family together to narrow it down, then confirm against the datasheet.

13 candidates 4 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
1SMA43A	ON	—	Public marking directory
2SC3929-T	PANASONIC ^*	SOT-323	Public marking directory
BSS139	INFINEON	SOT-23	Public marking directory
SDMG0340L	DIODES	—	Public marking directory
2SA1036KPT-P	—	SOT-23 16ta - 3a Chm	Public marking directory
2SC2405-T	—	SOT-23	Public marking directory
ASM812MEUS	—	SOT-143	Public marking directory
KIC7S08FU	—	SOT-353	Public marking directory
P4SMA56C	—	DO-214AC	Public marking directory
P4SMAJ180A	—	DO-214AB	Public marking directory
R1122N371B	—	SOT-23-5	Public marking directory
XC6127C44GNR	—	SSOT-24	Public marking directory
XC6223C34BNR-G	—	SSOT-24	Public marking directory

How we narrow this down

Package first — SOT-23 vs SOD-123 vs SC-59 eliminates most candidates immediately.
Pin count and body size — a 3-pin SOT-23 LDO cannot be a 6-pin dual transistor.
Marking style — laser-marked parts are usually newer production; ink marking often indicates older or second-source vendors.
Circuits around it — a part sitting on a rail with an inductor is a regulator, not a diode.
Datasheet check — every credible candidate lists its marking scheme in the “marking information” section.

FAQ

Same code, several parts — which one do I actually have? Compare package + pin count + surrounding circuit; if it still fits two parts, request a sample verification before production.
Can I substitute between the candidates? No — the same marking may sit on electrically different parts. Always match the electrical spec sheet, not just the marking.
Where do these mappings come from? Public SMD marking directories and historical stock tables; each row keeps its source so you can trace it.

Other codes starting with “S”

S14 S2 S4 S6 SAM SAY SEI SIL SIX SK

Still not sure what the part is?

Send the code, package and a photo through the BOM hub — our engineers cross-check it against datasheets and sourcing records.

How these mappings are compiled: public SMD marking directories plus our own stock records. Each row keeps its original reference internally, so any mapping can be traced on request. ^* Manufacturer derived from the part-number family (some directory entries carry no manufacturer) — treat it as a lead, not a datasheet fact. Markings are indicative only — confirm with the physical batch marking and the original datasheet before ordering.