Power Quality

Silicon Laboratories Introduces Small, Low Loss AC Current Sensor

Silicon Laboratories Inc. announced what the company claims is the world’s smallest low-loss high-accuracy ac current sensors for a wide range of power applications. The Si8500 family measures up to 20A of current for control and protection in power systems and is suitable for a broad range of applications including ac-dc switching power supplies, isolated dc-dc supplies, motor control and electronic ballasts for lighting.

The patent pending Si8500 integrates the functional equivalent of a current transformer circuit into a tiny 4 x 4 x 1 mm QFN package, including the current transformer, blocking diode, burden resistor and output RC filter, decreasing board space by up to 75% and reducing enclosure volume requirements by up to 80%. The Si8500 family also integrates temperature and offset compensation circuitry to achieve what is claimed to be industry-leading measurement accuracy of +/- 5% with a 2Vpp full-scale output signal swing. To further save cost and board space, the Si8510 family offers a "ping-pong" output that enables one Si8510 to replace two current transformer circuits in full-bridge applications.

The Si8500 family is said to boost efficiency and performance in both custom and off-the-shelf ac-dc power supplies. By integrating the current sensor into silicon, the Si8500 architecture is said to provide greater than five times lower series resistance and over two times lower series inductance than traditional discrete implementations. These performance gains are claimed to translate directly into lower power dissipation, higher efficiency, lower noise and reduced power supply complexity.

The Si8500 family integrates auto-calibration circuitry that is said to improve manufacturability and reliability by eliminating measurement offset and temperature sensitivities found in discrete current sensor implementations. Discrete designs typically use current transformers that suffer from mechanical variations. These variations can cause manufacturability problems related to component placement issues, as well as excessive mechanical tolerances, leading to further manufacturing steps for calibration and proper operation. The Si8500 is also rated to operate from -40 to +125°C in a standard surface mount package, simplifying power supply designs.

"Silicon Labs’ current sensors eliminate the need for large current transformers and associated discrete components," said David Bresemann, Vice President of Silicon Laboratories. "We are continuing to expand our family of power products with unique architectures that use cutting edge mixed-signal design techniques. Customers recognize that our vast improvements in performance, footprint and efficiency will translate to greater functionality and better performance in a smaller space."

The Si8500 family is sampling now and pricing starts at $1.49 for 1K pieces.

Silicon Laboratories Inc.
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