Integrated bidirectional 3.4-MHz isolator for I2C features 7 channels

May 22, 2014 // By Graham Prophet
Akros is a fabless semiconductor supplier that specialises in Power-over-Ethernet. It has taken the signal isolation technology it developed for the control channels of PoE and packaged it as a dedicated isolator, that expands the company’s GreenEdge digital isolation technology into the PSE segment of the PoE market, enabling real-time energy management in network systems.

The AS1705 is the only such product to feature 3.4 MHz communication speed, Akros says. The AS1705 comprises a dual channel bidirectional I 2C digital isolator as well as five unidirectional channels of isolation. Each of the isolation channels are rated to provide 2.5 kV of galvanic isolation. On the bidirectional I 2C channels, the AS1705’s 3.4 MHz data rate provides the needed bandwidth for a system’s processor to dynamically monitor and control the power requirements for multiple PSE controllers within a system. This enables the system to allocate the precise amount of power required by each port while eliminating unnecessary power allocation, which in turn reduces system energy consumption.

The design uses capacitive coupling within the package, with the capacitive elements being integrated on to the two dice that are involved, to achieve the 2.5 kV rating.

The five unidirectional channels replace optocouplers or standalone unidirectional digital isolators and provide all of the isolated communication signals used by a PSE system, including system reset, PSE interrupt and three power good indicators from the system’s power supply units. The integrated functionality of the AS1705 enables it to replace: either one I 2C digital isolator and five optocouplers or one I 2C digital isolator and a five-channel unidirectional digital isolator. In both of these cases, the AS1705 reduces the PCB footprint of the isolation circuitry by 50%, simplifying board layout and reducing design time.

“The 3.4 MHz AS1705 isolator offers the highest speed solution for real-time network power diagnostics for PSE equipment,” said Elie Antoun, President & CEO of Akros Silicon. “This integrated digital isolator simultaneously solves the design challenges of increasing communication bandwidth over the isolation barrier while also reducing PCB area in 48 and 96 port Ethernet switches.” The part costs $2.30 (1000).

Akros Silicon;