PNDS / Marking codes / BU

Identify an unknown SMD part: marking code “BU”

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
2SD1005-U	NEC ^*	SOT-89	Public marking directory
BAT54	FSC	SOD-123	Public marking directory
BCX71GR	FERRANTI	SOT-23	Public marking directory
BCX71RG	SIEMENS	SOT-23	Public marking directory
BD4739G	ROHM ^*	—	Public marking directory
BZX399-C27	PHI	SOD-323	Public marking directory
BZX399-C27	PHI	SC-76/SOD323	Public marking directory
BZX399C27	PHI	SOD323	Public marking directory
DA228K	ROHM ^*	SOT-346	Public marking directory
DA228U	ROHM ^*	SOT-323	Public marking directory
P6SMBJ20C	LITTLE ^*	DO-214AA	Public marking directory
R1112N381A	RICOH ^*	SOT-23-5	Public marking directory
R3112Q181C	RICOH ^*	SC-82AB	Public marking directory
R5421N163F	RICOH ^*	SOT-23-6	Public marking directory
XC61119C15ANR-G	TOREX ^*	SSOT-24 26gh VD3 5c Tor	Public marking directory
XC6119C15ANR	TOREX ^*	SSOT-24	Public marking directory
Anode1	—	—	Public marking directory
BZT52H-C27	—	SOD123F	Public marking directory
P4SMA36	—	DO-214AC	Public marking directory
RT9169-38CV	—	SOT-23	Public marking directory
RT9169-39CX	—	SOT-89	Public marking directory
TV04A200K	—	DO-214AC	Public marking directory
TV06B200KB	—	DO-214AA	Public marking directory
UDZ33B	—	SOD-323	Public marking directory
XC6109C15AN	—	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 “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.