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Isolated current sense amplifier offers low signal delay

02 Sep 2015

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Silicon Labs has announced an isolated current sense amplifier that claims to offer robust isolation and the industry's highest bandwidth and lowest signal delay. The Si8920 isolated amplifier boasts an ideal current shunt measurement solution for power control systems operating in harsh environments such as industrial motor drives, solar inverters, high-voltage power converters, uninterruptible power supplies (UPS) and electric/hybrid-electric vehicle (EV/HEV) systems, detailed the company.


Fast, accurate current sensing is essential for all high-power systems and power converters with high-voltage stages. Measuring current on high-voltage rails (up to 1.2kV) with a galvanically-isolated amplifier provides critical information to the low-voltage controller that improves system response time and efficiency. The isolated amplifier provides a differential, low-voltage input scaled for connection to current shunt resistors, enabling the controller to make precise measurements of current on high-voltage rails while maintaining best-in-class electrical isolation, Silicon Labs added. The Si8920 device supports signal bandwidth up to 750kHz to ensure rapid, precise dc current measurement and accurate representation of the primary signal and harmonics.

The Si8920 uses Silicon Labs' CMOS-based isolation technology, which meets stringent UL, VDE, CQC and CSA standards, supports up to 5kV withstand and 1.2kV working voltage, and offers a wider operating temperature range, better noise immunity and longer lifetimes than competing isolation technologies. The Si8920 amplifier flaunts an offset drift down to 1µV/°C to ensure stable performance over diverse operating conditions, indicated the company.

The Si8920 also meets the product longevity requirements of industrial automation, green energy and Internet infrastructure equipment. Many power systems feature long lifetime warranties and are expected to operate for 25 years or more in the field. Isolation often can be a point of first failure and a lifetime-limiting device in many power systems. Traditional isolators, based on optocoupler technology, suffer from limited temperature range and can degrade with the external environment. In contrast, CMOS-based isolation components such as the Si8920 isolated amplifier operate over a full industrial temperature range and can support product lifetimes of up to 100 years, Silicon Labs continued.

The Si8920 promises very fast response time with up to 0.75µs signal delay across the isolation barrier, allowing power control systems to react rapidly to transient load conditions. Ultra-low signal delay enables control loops to respond quickly, resulting in a more efficient and stable system as the controller can take action sooner to maintain the desired performance. Low signal delay also enables the power system to make quick corrective responses to unusual, potentially dangerous events, which helps reduce equipment repair and maintenance costs.

The Si8920 isolated amplifier is available now in standard SOIC and DIP packages, which are easy to handle with automated assembly systems. Si8920 pricing in 10,000-unit quantities begins at $2.39. The Si8920ISO-KIT evaluation kit enables developers to connect quickly to a shunt resistor to evaluate Si8920 analogue isolation functionality including low-voltage differential input, response times, offset and gain characteristics.

Priced at $29, the Si8920ISO-KIT evaluation kit is available from Silicon Labs and authorised distributors.

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