Adafruit
Adafruit LTC4311 I2C Extender / Active Terminator - STEMMA QT / Qwiic
The Adafruit LTC4311 Active Terminator solves a common I2C problem: running long cables. Standard I2C is designed for short PCB-level connections, but cable ...
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
Jargon buster
Plain-language definitions for the technical terms used above.
- BME680
- A Bosch environmental sensor chip that measures temperature, humidity, air pressure, and gas-related air quality changes. Seeing BME680 tells you this breakout is built around a specific all-in-one sensor, so you can check library support, accuracy, and datasheet details for that chip.
- I2C
- I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.
- OLED
- OLED stands for organic light-emitting diode, a display type where each pixel produces its own light. It matters because OLED screens are thin, high-contrast and easy to read for small status displays, but they can be more sensitive to image burn-in than some other display types.
- PCB
- A printed circuit board is a rigid board with copper tracks that connect electronic parts without loose wires. For this kit, the PCBs also form the airplane shape, so they are both the circuit base and part of the finished model.
- Qwiic
- Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.
- STEMMA
- A plug-and-cable connection system used on some maker electronics boards to make wiring simpler. If a product uses STEMMA, you need the matching cable or connector type to plug it in without soldering.
- STEMMA QT
- A small plug-in connector system for I2C boards that lets you connect compatible sensors and controllers without soldering. It matters because it can make wiring faster and less error-prone, especially when adding several small modules to a project.
Related Tutorials
Free guides on learn.littlebird.com.au
