The Adafruit LTC4311 Active Terminator solves a common I2C problem: running long cables. Standard I2C is designed for short PCB-level connections, but cable capacitance and resistance degrade signals over distance. The LTC4311 watches the SDA and SCL lines and actively boosts pull-up current, restoring clean square-wave signals even over multi-metre cables.

Simply plug this board into your I2C bus at the start of the chain — no firmware, software, or configuration needed. In testing, it ran a 400 kHz OLED over 3 metres of phone wire with ease, and even drove a BME680 sensor over 30 metres of Ethernet cable at 100 kHz (~3000 pF round trip).

Key Features

• Active I2C Termination – Boosts pull-up current on SDA and SCL for clean signal edges over long cables
• Wide Voltage Range – Works with any bus voltage from 1.6 V to 5.5 V
• Up to 400 kHz – Supports standard and fast I2C clock speeds
• Cable Capacitance up to 4000 pF – Handles very long cable runs
• Zero Configuration – No firmware, software, or resistor tuning required; just plug in and go
• STEMMA QT / Qwiic – Solderless I2C connectors on both sides for easy daisy-chaining

Ideal For

• Running I2C sensors over long cables (1–30+ metres)
• Fixing unreliable I2C communication on extended buses
• Remote sensor installations connected by phone wire or Ethernet cable
• Any I2C project where cable capacitance is degrading signal quality

Package Contents

• 1× Adafruit LTC4311 I2C Extender / Active Terminator (STEMMA QT)

Resources

• What is STEMMA QT?