PCIM - ­Upgrade for Popular Isolation Family

Skyworks launched its Si86x family of capacitive isolators over ten years ago. It has proven popular with engineers over that time and the products are still selling well, but changes in demands from the industry have meant that newer solutions are required to fulfil them.

Emmanuel Onyema, Product Line Manager, Skyworks explains, “Isolators are always going to be needed, but the requirements of applications have changed in that time. Maybe five years ago, a CMTI of 100 kilovolts per microsecond would be considered excessive, but new applications can have noisier environments, and such a high level of noise immunity is now necessary. The new Si86Sx range is the successor of the Si86x, which has been widely used in many different applications, including the automotive, industrial, telecoms and automotive markets”.

Skyworks has focussed on capacitive isolation over the alternatives of optical and magnetic isolation technologies. Like the name suggests, capacitive isolation uses two conductors and a dielectric to block DC voltage while allowing necessary voltages to pass through. In power supplies, this means that the output voltage can be sensed on the secondary side and the data passed back through to the controller on the primary side to allow better voltage regulation. Capacitive isolation generally offers high bandwidth, 150 Mbps in the case of the Si86Sx range, to allow the circuit to react more quickly. It also has high isolation strength and is immune to magnetic noise.

Onyema explains the improvements in the new Si86Sx range, “The isolation barrier is better. We now can offer over 10 kV of surge immunity and 6 kV_RMS protection for 1 min, while the previous generation could withstand around 5 kV_RMS. That robust isolation barrier also helps to give better EMC tolerance. To withstand noise, the new range has a CMTI figure that has doubled from around 50 kV/μs to 100 kV/μs. We have also changed the input technology from TTL to CMOS to provide a higher voltage input range. A deglich function has been added to filter out spikes in signals that are shorter than 30 or 36 nanoseconds, depending on the part. The devices have a 0.25 mA/channel low-power mode and 750μA per side sleep mode to save energy. All those features are available in a package that is pin compatible with the Si86x range”.

There is a variety of devices available in the Si86Sx series, including options for single-, dual- and multi-channel operation. AEC-Q100 qualified automotive grade devices, which have been built using automotive-specific flows to address the robustness, enhanced EMC requirements and low defectivity required for those applications, are available for some part numbers. A variety of evaluation boards are also available.

https://cm-sitecore.skyworksinc.com/Products/Isolation/Si86Sx-Digital-Isolators