A dual-channel digital isolator in SOIC-8 that passes logic signals across a galvanic isolation barrier, a fast, reliable replacement for optocouplers. It carries two channels in opposite directions (one A-to-B, one B-to-A), each side powered from its own supply (VCC1, VCC2), with an isolation barrier rated to about 2.5 kVrms that breaks ground loops and protects low-voltage logic from a high-voltage or noisy domain. Built on a capacitive isolation core, it is faster (up to 150 Mbps depending on grade), lower power, and more stable over temperature and lifetime than an optocoupler. Common uses are isolated UART/SPI links, RS-485/CAN side isolation, and isolated control signals. The related ISO7220/7231/7241 offer other channel counts and directions.

Pinout

Pin	Name	Type	Function
1	VCC1	power_in	Power supply for side 1 (input for channel A, output for channel B). 2.8 V / 3.3 V / 5 V; independently referenced to GND1. Decouple locally with a 0.1 µF ceramic near the pin.
2	OUTA	output	Buffered CMOS output of channel A on side 1 of the isolation barrier (isolated copy of INA on side 2). 4 mA drive; output high/low tracks VCC1.
3	INB	input	Digital input of channel B on side 1. A-, B-, and C-option devices apply a TTL input threshold (VIH ≥ 2 V, VIL ≤ 0.8 V) with input noise filtering; M-option uses a CMOS threshold (0.7·VCC / 0.3·VCC). If undriven for >4 µs the failsafe drives the isolated output high.
4	GND1	power_in	Ground reference for side 1 (VCC1 domain). Galvanically isolated from GND2 by the SiO₂ barrier.
5	GND2	power_in	Ground reference for side 2 (VCC2 domain). Galvanically isolated from GND1 by the SiO₂ barrier.
6	OUTB	output	Buffered CMOS output of channel B on side 2 (isolated copy of INB on side 1). 4 mA drive; output high/low tracks VCC2.
7	INA	input	Digital input of channel A on side 2. A-, B-, and C-option devices use TTL thresholds with input noise filtering; M-option uses CMOS thresholds. Failsafe forces the isolated output high when INA is undriven for >4 µs.
8	VCC2	power_in	Power supply for side 2 (input for channel A, output for channel B). 2.8 V / 3.3 V / 5 V; independently referenced to GND2. Decouple locally with a 0.1 µF ceramic near the pin.

Key specifications

Parameter	Value
Type	2-channel digital isolator
Channels	2 (one each direction)
Isolation	~2.5 kVrms barrier (capacitive)
Data rate	up to 150 Mbps (by grade)
Supplies	VCC1 + VCC2 (independent)
Advantage	faster + longer-life than optocoupler
Supply voltage	3.3-5 V each side
Package	SOIC-8

Ordering variants

Same part, different packaging or reel option.

ISO7221CD (SOIC-8)
ISO7221AD (SOIC-8)

CAD (KiCad official)

Symbol: ISO7221 (generated from datasheet; KiCad has no symbol)
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D)

Provenance

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

Datasheet: Texas Instruments datasheet (39 pp, sha256 b74a541cca2d68e0, retrieved 2026-08-17, tier: manufacturer)
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