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TCA6408A 8-Bit I2C I/O Expander

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by Ray

8-bit I2C I/O expander with configurable direction, polarity inversion, and interrupt.

gpio-expanderi2cio-expander8-bitinterrupttitssop-16
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TCA6408A

Texas Instruments · I/O Expander · TSSOP-16

The TCA6408A is an 8-bit I2C I/O expander. Each pin is independently configurable as input or output, with optional input-polarity inversion, and an open-drain interrupt output flags changes on inputs. A reset input and a single address pin round it out, making it a flexible way to add general-purpose I/O over I2C.

Pinout

Pin Name Type Function
1 VCCI power_in Supply voltage for the I2C side (1.65-5.5 V). Connect directly to the VCC of the external I2C controller; provides voltage-level translation between the I2C bus and the P-ports.
2 ADDR input Hardware I2C slave-address select input. Tie directly to VCCP for one address or to GND for the other; VIH ≥ 0.7 x VCCP.
3 RESET input Active-low reset input. Drive low to reset the device registers to their default (all P-ports as inputs). Connect to VCCI through a pull-up resistor if no active drive is used.
4 P0 bidirectional P-port 0. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up. IOL up to 25 mA (P-port continuous 50 mA max).
5 P1 bidirectional P-port 1. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up.
6 P2 bidirectional P-port 2. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up.
7 P3 bidirectional P-port 3. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up.
8 GND power_in Device ground reference. Continuous current through GND rated to 200 mA.
9 P4 bidirectional P-port 4. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up.
10 P5 bidirectional P-port 5. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up.
11 P6 bidirectional P-port 6. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up.
12 P7 bidirectional P-port 7. Push-pull general-purpose I/O referenced to VCCP; configured as an input at power-up.
13 INT output Open-drain active-low interrupt output. Asserted when any P-port input changes state. Connect to VCCI through a pull-up resistor.
14 SCL input I2C serial clock input. Connect to VCCI through a pull-up resistor; supports 100-kHz Standard-mode and 400-kHz Fast-mode.
15 SDA bidirectional I2C serial data bus (open-drain). Connect to VCCI through a pull-up resistor; IOL up to 25 mA.
16 VCCP power_in Supply voltage for the P-port side (1.65-5.5 V). Sets the logic level of P0-P7; continuous current through VCCP rated to 160 mA.

Key specifications

Parameter Value
Type 8-bit I2C I/O expander
I/O 8, per-pin direction
Interface I2C (up to 400 kHz)
Features Polarity inversion, interrupt, reset
Addressing 1 address pin (2 devices)
Supply voltage 1.65 V to 5.5 V
Operating temperature -40 C to 85 C

Ordering variants

Same part, different packaging or reel option.

  • TCA6408APW
  • TCA6408APWR
  • TCA6408ARGT
  • TCA6408ARGTR
  • TCA6408ARSV
  • TCA6408ARSVR

CAD (KiCad official)

  • Symbol: tca6408a.kicad_sym
  • Footprint: tca6408a.kicad_mod
  • 3D model: TSSOP-16 body from KiCad Package_SO/TSSOP-16_4.4x5mm_P0.65mm.

Provenance

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

  • Datasheet: Texas Instruments datasheet (50 pp, sha256 4e444553aa8bf678, 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