Isolators for hybrid cars

The simple I2C bus connects controllers and peripheral devices. In automotive and especially hybrid electric vehicle applications, controllers or peripherals are isolated from the bus to avoid interference or harmful voltage levels. Usually, optocouplers are being used, but this increases the cost and complexity disproportionally. Digital isolators have the potential to simplify I2C design in electric and hybrid-electric vehicles.

The cost-effective  I2C bus uses bidirectional lines to transmit and receive signals over the same wire, allowing two-wire signalling of clock and data. Optocoupler-based isolation increases cost and complexity of the I2C interface because unidirectional optocouplers must be accommodated by separating each of the two bidirectional I2C channels into two unidirectional channels. The resulting four unidirectional channels are then each isolated with an optocoupler and recombined into two bidirectional channels. The additional circuitry associated with the bidirectional/unidirectional conversions and the isolation of the four unidirectional channels adds complexity and cost that offset the intended benefits of the I2C bus.


A single component, the isolator »ADuM1250W« from Analog Devices, directly provides bidirectional isolation to both of the I2C lines. This small device is supposed to ensure the signal integrity of the bidirectional I2C bus while reducing component count, cost, board space, and complexity.


It is based on ADI’s proprietary digital isolation technology »iCoupler«. The hot swappable, dual I2C digital isolator ADuM1250W in 8-lead SOIC package potentially reduces board space by as much as 80% by eliminating optocouplers and support circuitry.


It operates with 1 MHz and 3.0- to 5.5-V supply/logic levels and carries an AEC-Q100 qualified automotive temperature rating between -40°C and +125°C.