BL1551B from BL Shanghai Belling, in a SC-70-6. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	A1	bidirectional	Analog switch throw terminal 1. Bidirectional data port; connected to common terminal B when ENB is HIGH. Signal range 0V to VCC; RON ~2.7Ω at VCC=5V.
2	GND	power_in	Ground return for the device.
3	A2	bidirectional	Analog switch throw terminal 2. Bidirectional data port; connected to common terminal B when ENB is LOW. Signal range 0V to VCC; RON ~2.7Ω at VCC=5V.
4	B	bidirectional	Analog switch common (pole) terminal. Bidirectional data port routed to either A1 or A2 under control of ENB. Signal range 0V to VCC.
5	VCC	power_in	Positive supply input, 1.8V to 5.5V operating range (6V absolute max). Bypass with a 0.1µF capacitor to GND.
6	ENB	input	Digital logic control input selecting the switch position. ENB=HIGH connects A1 to B; ENB=LOW connects A2 to B. TTL/CMOS compatible (VIH ≥ 1.5V, VIL ≤ 0.6V at VCC=5V). Must not be left floating.

Key specifications

Parameter	Value
Manufacturer	BL Shanghai Belling
Package	SC-70-6
Category	Interface
Pins	6

Ordering variants

BL1551B

CAD (KiCad official)

Symbol: BL1551B
Footprint: Package_TO_SOT_SMD:SOT-363_SC-70-6
3D model: SC-70-6 (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: BL Shanghai Belling datasheet (10 pp, sha256 e066dbc07f7b36a0, retrieved 2026-08-17, tier: lcsc)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF