I²C Isolation

Isolating the I²C bus can be problematic due to its bidirectional operation. The typical discrete I²C isolation approach requires four optocouplers for isolation, plus complex analog circuits to support anti-latch and glitch suppression. This isolation circuitry burdens the I²C interface with increased cost and board area, and lower reliability.

The Silicon Labs Si8400 series of I²C digital isolators are single-chip solutions for isolating the I²C bus. These products are based on Silicon Labs’ Industry-leading and patented digital isolation technology that delivers substantial gains in performance, reliability, cost and power consumption compared to optocoupler-based solutions. Because they are isolated, these products are also useful as I²C extenders, where they can isolate sections of the I²C bus that are heavily loaded, preserving signal integrity and reducing pull-up resistor power losses.

Watch the I²C and SMBus Isolation Video

I²C Isolation Applications

The Si840x digital isolator devices are suitable for use in a wide range of I²C applications where galvanic isolation is required:

• Power-over-Ethernet (PoE)
• Power Sourcing Equipment (PSE)
• Switches and midspans
• Power supplies
• Isolated SMBus or PMBus interfaces used in blade servers and other hot swappable systems

I²C Isolation Products

The Si8400 digital isolator features two bidirectional channels (for SDA and SCL), while the Si8405 digital isolator offers two additional isolated, uni-directional channels for other system signals, such as a reset or interrupt, independent of the I²C data and clock. Both the Si8400 and Si8405 isolators support up to 2 Mbps I²C bus data rate, and offer up to 2.5kV isolation, industrial temperature range (-40 to 125 °C), and an input voltage supply range from 3 to 5 V. The Si8400 isolator is available in narrow body SOIC-8 package, and is footprint compatible with common devices. The Si8405 isolator is available in the narrow body SOIC-16 package.

Learn more on why to choose Si840x digital isolators.

Serial Data, Serial Clock (ASDA, ASCL)  

Part Number	Serial Data	Serial Clock	Data Channels	Maximum I²C Clock Rate (MHz)	Isolation Rating	Package		Buy
			Fwd, Rev			NB SOIC8	NB SOIC16
Si8400AA-B-IS	•	•	0,0	1.7	1.0 kVrms	•
Si8400AB-B-IS	•	•	0,0	1.7	2.5 kVrms	•
Si8401AA-B-IS	•		Clock	1.7	1.0 kVrms	•
Si8401AB-B-IS	•		Clock	1.7	2.5 kVrms	•

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 Serial Data, Serial Clock + 2-Channel Uni-directional 

Part Number	Serial Data	Serial Clock	Data Channels	Maximum I²C Clock Rate (MHz)	Isolation Rating	Package		Buy
			Fwd, Rev			NB SOIC8	NB SOIC16
Si8405AA-B-IS1	•	•	1,1	1.7	1.0 kVrms		•
Si8405AB-B-IS1	•	•	1,1	1.7	2.5 kVrms		•