PNDS / Marking codes / B4

Identify an unknown SMD part: marking code “B4”

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 20 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
2SC4175-4	NEC ^*	SOT-323	Public marking directory
BAT54W	NXP	SOT-323	Public marking directory
BD4733G	ROHM ^*	—	Public marking directory
BSV52R	PHI	SOT-23	Public marking directory
BZT52H-C2V7	PHI	SOD123F	Public marking directory
BZX399-C2V4	PHI	SOD-323	Public marking directory
BZX399-C2V4	PHI	SC-76/SOD323	Public marking directory
BZX399C2V4	PHI	SOD323	Public marking directory
FSS25	SANYO ^*	DO-214AA	Public marking directory
HSMS-2814	AGILENT	SOT-23	Public marking directory
HSMS-281F	AGILENT	SOT-323	Public marking directory
LM4667ITL	NSC	BGA-9	Public marking directory
LM4667ITLX	NSC	BGA-9	Public marking directory
MBR0540	FSC	SOD-123	Public marking directory
MBRA140	ON ^*	DO-214AC	Public marking directory
MMSZ5223B	DIODES	SOD-123	Public marking directory
R3111N142A	RICOH ^*	SOT-23	Public marking directory
R3113D241A	RICOH ^*	—	Public marking directory
R3114Q211A	RICOH ^*	SC-82AB	Public marking directory
R5421N133C	RICOH ^*	SOT-23-6	Public marking directory
2SC1621-4	—	SOT-23	Public marking directory
2SC4987-4	—	SMCP	Public marking directory
AP432AW	—	SOT-23-3L	Public marking directory
BAS70SPT	—	SC-59 16dl - 3a Chm	Public marking directory
BZX884-C3V3	—	SOD-882	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 B5 B6 B7 B8 B9 BA BB

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.