PNDS / Marking codes / BY

Identify an unknown SMD part: marking code “BY”

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.

25 candidates 16 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
2SA1200-Y	TOS ^*	SOT-89	Public marking directory
2SC4396	TOS ^*	SOT-323	Public marking directory
2SC5342U-Y	TOS ^*	SOT-323 16ta - 3a Auk	Public marking directory
2SC5342UF-Y	TOS ^*	SOT-323F 18ta - 3a Auk	Public marking directory
BCW71KR	PHI	SOT23R	Public marking directory
BCX71RK	SIEMENS	SOT-23	Public marking directory
BD4743G	ROHM ^*	—	Public marking directory
BZX399-C39	PHI	SOD-323	Public marking directory
BZX399-C39	PHI	SC-76/SOD323	Public marking directory
BZX399C39	PHI	SOD323	Public marking directory
MMBZ5255B	FS	SOT-23 16dc - 3a Lge	Public marking directory
P6SMBJ24C	LITTLE ^*	DO-214AA	Public marking directory
R5421N151F	RICOH ^*	SOT-23-6	Public marking directory
TC1015-1.8VRX	MIC ^*	SOT-23-5	Public marking directory
XC61119C18ANR-G	TOREX ^*	SSOT-24 26gh VD3 5c Tor	Public marking directory
XC6119C18ANR	TOREX ^*	SSOT-24	Public marking directory
2SC3395	—	CP 16ta - 3a San	Public marking directory
2SK1334	—	SOT-89	Public marking directory
BZT52H-C39	—	SOD123F	Public marking directory
Cathode1	—	—	Public marking directory
GS6332UR19D1	—	SOT-23	Public marking directory
KTA1660-Y	—	SOT-89	Public marking directory
MMSZ4690	—	SOD-123	Public marking directory
P4SMA43	—	DO-214AC	Public marking directory
RT9169-42CV	—	SOT-23	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 “B”

B1 B2 B3 B4 B5 B6 B7 B8 B9 BA

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.