PNDS / Marking codes / 31

Identify an unknown SMD part: marking code “31”

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.

22 candidates 12 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
2SC5663PT	ROHM ^*	SOT-723 18ta - 3a Chm	Public marking directory
2SC5663TPT	ROHM ^*	SOT-416 16ta - 3a Chm	Public marking directory
MMBD1402	NSC	SOT23	Public marking directory
MUN5331DW1	MOT	SOT363	Public marking directory
PD3S140	DIODES	—	Public marking directory
PDTA124XE	PHI	SOT-416	Public marking directory
PDTA124XE	PHI	SC-75/SOT416	Public marking directory
PDTA124XEF	PHI	SOT-490	Public marking directory
PDTA124XEF	PHI	SC-89/SOT490	Public marking directory
R3111Q311B	RICOH ^*	SC-82AB	Public marking directory
RN5RF31AA	RICOH ^*	SOT-23-5	Public marking directory
RN5RZ31AA	RICOH ^*	SOT-23-5	Public marking directory
CHT5663M1PT	—	FBPT-723 17ta - 9a Chm	Public marking directory
ELM9831BB	—	SOT-23 16cg VR1 3d Elm	Public marking directory
HMSZ5231B	—	SOD-323	Public marking directory
MUN5331DW	—	SOT-363	Public marking directory
R1163D181E5	—	—	Public marking directory
R1223N182F	—	SOT-23-5	Public marking directory
UTC8131	—	SOT-89	Public marking directory
XC6213B312NR	—	SSOT-24	Public marking directory
XC6221C39BNR	—	SSOT-24	Public marking directory
ZD5231BS2	—	SOD-323	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 “3”

30 33 36 37 39 3A 3B 3E 3D 32

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.