Adds sixteen general-purpose I/O pins over I2C, arranged as two 8-bit ports (P0x and P1x), each pin set as input or output through a configuration register. An open-drain INT output flags a change on any input so the host is told which pin moved without polling, and three address pins put up to eight devices on one bus. It runs from 1.65 to 5.5 V. The 16-bit sibling of the TCA9534, for panels of buttons, LEDs, and enable lines.

Pinout

Pin	Name	Type	Function
1	INT	output	Active-low, open-drain interrupt output. Asserts when any P-port input changes state; connect to VCC through an external pull-up resistor. IOL up to 3 mA (VOL = 0.4 V).
2	A1	input	I2C slave address input bit 1. Tie directly to VCC or GND to set the device address; combined with A0/A2 selects one of eight bus addresses.
3	A2	input	I2C slave address input bit 2. Tie directly to VCC or GND to set the device address.
4	P00	bidirectional	Port 0 bit 0. Push-pull I/O; configured as input at power-on. If left unused when configured as input, tie to VCC or GND through ~10 kΩ.
5	P01	bidirectional	Port 0 bit 1. Push-pull I/O; configured as input at power-on.
6	P02	bidirectional	Port 0 bit 2. Push-pull I/O; configured as input at power-on.
7	P03	bidirectional	Port 0 bit 3. Push-pull I/O; configured as input at power-on.
8	P04	bidirectional	Port 0 bit 4. Push-pull I/O; configured as input at power-on.
9	P05	bidirectional	Port 0 bit 5. Push-pull I/O; configured as input at power-on.
10	P06	bidirectional	Port 0 bit 6. Push-pull I/O; configured as input at power-on.
11	P07	bidirectional	Port 0 bit 7. Push-pull I/O; configured as input at power-on. Octal P07-P00 total drive limited to 80 mA.
12	GND	power_in	Device ground. Continuous current through GND limited to 250 mA.
13	P10	bidirectional	Port 1 bit 0. Push-pull I/O; configured as input at power-on.
14	P11	bidirectional	Port 1 bit 1. Push-pull I/O; configured as input at power-on.
15	P12	bidirectional	Port 1 bit 2. Push-pull I/O; configured as input at power-on.
16	P13	bidirectional	Port 1 bit 3. Push-pull I/O; configured as input at power-on.
17	P14	bidirectional	Port 1 bit 4. Push-pull I/O; configured as input at power-on.
18	P15	bidirectional	Port 1 bit 5. Push-pull I/O; configured as input at power-on.
19	P16	bidirectional	Port 1 bit 6. Push-pull I/O; configured as input at power-on.
20	P17	bidirectional	Port 1 bit 7. Push-pull I/O; configured as input at power-on. Octal P17-P10 total drive limited to 80 mA.
21	A0	input	I2C slave address input bit 0. Tie directly to VCC or GND to set the device address.
22	SCL	input	I2C serial clock input. Connect to VCC through a pull-up resistor. Supports Standard (100 kHz) and Fast (400 kHz) modes.
23	SDA	bidirectional	I2C serial data bus. Open-drain; connect to VCC through a pull-up resistor. IOL up to 3 mA (VOL = 0.4 V).
24	VCC	power_in	Supply voltage, 1.65 V to 5.5 V. Continuous current through VCC limited to 160 mA. Recommended decoupling with a bypass capacitor near the pin.

Key specifications

Parameter	Value
Type	16-bit I2C I/O expander
Interface	I2C (up to 400 kHz)
I/O	16 pins (two 8-bit ports)
Interrupt	INT output (interrupt-on-change)
Addresses	8 (A0-A2)
Supply	1.65-5.5 V
Package	SSOP-24

Ordering variants

Same part, different packaging or reel option.

TCA9535DBR (SSOP-24)
TCA9535PWR (TSSOP-24)
TCA9535RTWR (VQFN-24)

CAD (KiCad official)

Symbol: Interface_Expansion:TCA9535DBR (KiCad official)
Footprint: Package_SO:SSOP-24_5.3x8.2mm_P0.65mm
3D model: SSOP-24 (KiCad packages3D, STEP)

Provenance

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

Datasheet: Texas Instruments datasheet (47 pp, sha256 413a6d0c3d8f1a2e, 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