Adds eight general-purpose I/O pins over I2C, each set as input or output through a configuration register. An open-drain INT output flags a change on any input pin, so the host is told which line moved without polling, and three address pins (A0-A2) put up to eight devices on one bus. It runs from 1.65 to 5.5 V, so it bridges different logic domains. A more capable alternative to the PCF8574 with a proper config register and interrupt.

Pinout

Pin	Name	Type	Function
1	A0	input	I2C hardware address input bit 0. Tie directly to VCC or GND to set the device slave address. Allows up to eight TCA9534 devices on the same I2C bus.
2	A1	input	I2C hardware address input bit 1. Tie directly to VCC or GND to set the device slave address.
3	A2	input	I2C hardware address input bit 2. Tie directly to VCC or GND to set the device slave address.
4	P0	bidirectional	P-port I/O bit 0. Push-pull output structure; configured as an input at power-on. IOH max -10 mA, IOL up to 25 mA (Tj <= 65 C).
5	P1	bidirectional	P-port I/O bit 1. Push-pull; configured as an input at power-on.
6	P2	bidirectional	P-port I/O bit 2. Push-pull; configured as an input at power-on.
7	P3	bidirectional	P-port I/O bit 3. Push-pull; configured as an input at power-on.
8	GND	power_in	Ground reference for the device.
9	P4	bidirectional	P-port I/O bit 4. Push-pull; configured as an input at power-on.
10	P5	bidirectional	P-port I/O bit 5. Push-pull; configured as an input at power-on.
11	P6	bidirectional	P-port I/O bit 6. Push-pull; configured as an input at power-on.
12	P7	bidirectional	P-port I/O bit 7. Push-pull; configured as an input at power-on.
13	INT	output	Active-low open-drain interrupt output. Asserted when an input port changes state; connect to VCC through a pullup resistor. IOL must be externally limited to 7 mA max.
14	SCL	input	I2C serial clock input. Connect to VCC through a pullup resistor. Supports 100-kHz and 400-kHz operation.
15	SDA	bidirectional	I2C serial data line, open-drain bidirectional. Connect to VCC through a pullup resistor. IOL up to 8 mA at VOL = 0.5 V.
16	VCC	power_in	Supply voltage input, 1.65 V to 5.5 V. Bypass locally to GND with a decoupling capacitor.

Key specifications

Parameter	Value
Type	8-bit I2C I/O expander
Interface	I2C (up to 400 kHz)
I/O	8 pins (P0-P7)
Interrupt	INT output (interrupt-on-change)
Addresses	8 (A0-A2)
Supply	1.65-5.5 V
Package	TSSOP-16

Ordering variants

Same part, different packaging or reel option.

TCA9534PWR (TSSOP-16)
TCA9534ADWR (SOIC-16, variant address)
TCA9534RGTR (VQFN-16)

CAD (KiCad official)

Symbol: Interface_Expansion:TCA9534 (KiCad official)
Footprint: Package_SO:TSSOP-16_4.4x5mm_P0.65mm
3D model: TSSOP-16 (KiCad packages3D, STEP)

Provenance

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

Datasheet: Texas Instruments datasheet (42 pp, sha256 797c1fc96502df7c, 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