UM3308UK from Union Semiconductor, in a TSSOP-20. 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	Input/Output 1 on the A-port side. Referenced to VCCA (1.2-3.6 V) and paired with B1 as one bidirectional level-translated channel.
2	VCCA	power_in	A-port supply voltage. Accepts 1.2 V to 3.6 V (absolute range 1.1 V ≤ VCCA ≤ 3.6 V) and must be ≤ VCCB. Sets the logic level for the A-side I/Os and the OE input.
3	A2	bidirectional	Input/Output 2 on the A-port side. Referenced to VCCA and paired with B2.
4	A3	bidirectional	Input/Output 3 on the A-port side. Referenced to VCCA and paired with B3.
5	A4	bidirectional	Input/Output 4 on the A-port side. Referenced to VCCA and paired with B4.
6	A5	bidirectional	Input/Output 5 on the A-port side. Referenced to VCCA and paired with B5.
7	A6	bidirectional	Input/Output 6 on the A-port side. Referenced to VCCA and paired with B6.
8	A7	bidirectional	Input/Output 7 on the A-port side. Referenced to VCCA and paired with B7.
9	A8	bidirectional	Input/Output 8 on the A-port side. Referenced to VCCA and paired with B8.
10	OE	input	3-state Output Enable input, referenced to VCCA. Pulling OE low places all A and B outputs in the high-impedance state. Should be tied to GND through a pull-down resistor during power up/down to guarantee Hi-Z; VIH ≥ VCCA×0.65, VIL ≤ VCCA×0.35.
11	GND	power_in	Device ground return for both A-side and B-side supply currents.
12	B8	bidirectional	Input/Output 8 on the B-port side. Referenced to VCCB and paired with A8. Includes ±15 kV ESD protection.
13	B7	bidirectional	Input/Output 7 on the B-port side. Referenced to VCCB and paired with A7. Includes ±15 kV ESD protection.
14	B6	bidirectional	Input/Output 6 on the B-port side. Referenced to VCCB and paired with A6. Includes ±15 kV ESD protection.
15	B5	bidirectional	Input/Output 5 on the B-port side. Referenced to VCCB and paired with A5. Includes ±15 kV ESD protection.
16	B4	bidirectional	Input/Output 4 on the B-port side. Referenced to VCCB and paired with A4. Includes ±15 kV ESD protection.
17	B3	bidirectional	Input/Output 3 on the B-port side. Referenced to VCCB and paired with A3. Includes ±15 kV ESD protection.
18	B2	bidirectional	Input/Output 2 on the B-port side. Referenced to VCCB and paired with A2. Includes ±15 kV ESD protection.
19	VCCB	power_in	B-port supply voltage. Accepts 1.65 V to 5.5 V and must be ≥ VCCA. Sets the logic level for the B-side I/Os.
20	B1	bidirectional	Input/Output 1 on the B-port side. Referenced to VCCB and paired with A1. Includes ±15 kV ESD protection.

Key specifications

Parameter	Value
Manufacturer	Union Semiconductor
Package	TSSOP-20
Category	Logic
Pins	20

Ordering variants

Same part, different packaging or reel option.

UM3308UK
UM3308UKH
UM3308UKQA
UM3308UKQB

CAD (KiCad official)

Symbol: UM3308UK
Footprint: Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm
3D model: TSSOP-20 (KiCad packages3D, STEP)

Provenance

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

Datasheet: Union Semiconductor datasheet (18 pp, sha256 def9f2167aebfccc, 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