Philips Semiconductor developed the I2C bus to connect integrated circuits domiciled on a single printed circuit board. The evolution of the standard has since ensured that the bus is used in off-PCB applications. In this case, galvanic insulation can be incredibly beneficial.

With the ADuM1252, Analog Devices provides an easy-to-use way to achieve this. The component fits between the various I2C devices as shown.

The two sides are galvanically isolated once the ADuM1252 is part of the circuit. Following the datasheet, a long-term resistance of more than 400 V can be withstood. In terms of short-term robustness, Analog Devices promises even more:

  • Withstands ±10kV Surge per IEC 61000-4-5
  • Creepage and Clearance
  • 8-Narrow SOIC: 4mm

Due to these excellent performance metrics, the component will also be certified by various industry-standard bodies. Due to the freshness, these certification tests are still ongoing. However, circuit designers will soon be able to look forward to the following:

  • IEC60747-17 (Pending)
  • Reinforced V IORM Narrow SOIC: 630V PEAK
  • UL 1577 (Pending)
  • 8-Narrow SOIC: 3000V RMS for 1min
  • IEC/EN/CSA 62368-1 (Pending)
  • IEC/EN/CSA 61010-1 (Pending)
  • CAN/CSA-C22.2 No. 14-18 (Pending)

Advanced level translation and high drive capability

Due to the breadth of the I2C standard, circuit designers are often faced with a situation where sensors operating at multiple different voltage levels have to coexist on one bus. While I2C voltage converters are not particularly difficult to construct, users of the ADuM1252 are provided with such a component free of charge.

As shown in the figure, both sides can be supplied with various voltage limits; in particular, Analog Devices permits a DC voltage supply range from 1V71 to 5V1. Furthermore, high-drive sink currents are permitted: side one permits a respectable five milliamperes, while side two is able to handle 50 milliamperes. Small pull-up resistors can thus be used for bus biasing, ensuring good performance even as cable lengths and the associated cable capacities increase.

Support for high-speed I2C buses

While Phillips Semiconductor initially specified a maximum speed of 400 kHz, semiconductor technology advancements led to significantly faster I2C buses. In the case of the ADuM1252, Analog Devices promises a maximum transfer speed of up to 2 MHz - thereby ensuring that fast sensors can also be protected.

In addition to that, the galvanic insulator component comes with hot plug support. This means that dynamic reconfiguration of the bus network does not lead to unnecessary loading during device bring-up.

Conclusion

If galvanic insulation and/or voltage translation are needed on an I2C bus, the ADuM1252 is a comfortable component to use.