Extender / Terminator bus I2C, LTC4311

LTC4311 I2C Extender / Active terminator

I2C bus (Inter-Integrated-Circuit communications) is a very common and useful bus. It has been designed for short distances bus (on PCB or Sub assembly) in a project. Usual distance should be quite smaller than a meter. Over a longer distance, the bus signal are distorded and cannot be interpreted anymore by the I2C device. Signal distortion is caused by line capacitance and cross-talking. As the capacitance increase with bus length, the communication problems may increase as the bus length. This usually leads you to slow down the bus clock under 100KHz, sometime even at 1 KHz!

Thank to the LTC4311 the I2C run over a meter long cable, or even longer! The LTC4311 is an active terminator that will make its possible to actively rectify the shape of the signal! Thank to its capability, you will be able to maintain full bus speed over longer distances. That's magic!

Using this board is easy: connect the breakout at the begining of the bus (on a short bus, you can also place it at the end of the bus).
When the chip is powered and enabled, it watches the SCL and SDA lines. When it sees them raising up by the I2C pull-up resistors then it get activated and inject some current in the lines to boost up the signal to the power rail voltage.

Thanks to the LTC4311, you can maintain a high clock speed on the bus without having to tweak the pull-up resistors here and there on the long cables of your I2C bus. You can expect a 400 KHz bus over 3 meters on without problem. If you do slow down the bus clock at 100KHz then the bus range could possibly be increased up to 30m of ethernet cable (about 3000pF round trip!) and add an I2C device at the other end.

The breakout support any bus voltage from 1.6V to 5.5V, 400 KHz SCL speed, with cables up to 4000pF. Just plug be breakout on the bus an let him do its magical stuff.

To use the board: simply plug the power, ground, SCL and SDA connectors into your bus.

The breakout also fits Qwiic/StemmaQT connector if you want to use them to make fast connexion.

Technical details

• Wide Supply Voltage: 1.6V to 5.5V
• Improves I2C Bus Rise Time Transition
• Ensures Data Integrity on the I2C Bus.
• Improves Low State Noise Margin
• Up to 400kHz Operation
• Auto Detect Low Power Standby Mode
• Low (<5μA) Supply Current Shutdown
• Does Not Load Bus When Disabled or Powered Down
• Strong Slew Limited Pull-up Current
• +/- 8 kV Human Body Model ESD Ruggedness