PNDS / Marking codes / S1

Identify an unknown SMD part: marking code “S1”

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.

20 candidates 12 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
1PS76SB10	PHI	SOD323	Public marking directory
1PS76SB21	PHI	SOD-323	Public marking directory
1PS76SB21	PHI	SC-76/SOD323	Public marking directory
1SS239	TOS ^*	SOD-323	Public marking directory
BBY31	PHI	SOT-23	Public marking directory
HSMP-3881	HP	SOT23	Public marking directory
R1121N311B	RICOH ^*	SOT-23-5	Public marking directory
R3116Q181C	RICOH ^*	SC-82AB	Public marking directory
SD101AW	DIODES	SOD-123	Public marking directory
SD101AWS	MCC	SOD-323	Public marking directory
SD101BW	MCC	SOD-123	Public marking directory
SST271	SILICONIX-VISHAY	SOT-23	Public marking directory
BFG310/XR	—	SOT-143R	Public marking directory
ELM7631HCB	—	SOT-23 16vdc VD7 3d Elm	Public marking directory
ELM9741CAB	—	SOT-89	Public marking directory
FS2A	—	DO-214AA	Public marking directory
R1131D111D	—	—	Public marking directory
R1225N602C	—	SOT-23-6W 33so	Public marking directory
R3130N44DA	—	SOT-23	Public marking directory
RP104Q281D5	—	SC-82AB	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.