Silicon Labs' New AC Current Sensors Replace Bulky Transformers

The Si85xx ac current sensors provide a more reliable, cost-effective alternative to antiquated transformers for today's modern power delivery systems. Traditional transformers are large, bulky magnetic components that contribute significant supply losses and have parasitics that complicate system design. The highly integrated ISOpro ac current sensors feature a sophisticated architecture that minimizes the need for costly discrete components for filtering and reset circuitry. An available small-footprint QFN package eases PCB board space constraints with a small 4x4x1 mm profile.



The Si85xx sensors are available in 5 A, 10 A and 20 A versions and provide a large output signal level of 2.0 V at full-scale output range, eliminating the need for an external amplifier. A ping-pong output mode enables one sensor to replace two current transformers and associated components in full-bridge applications, reducing board footprint by more than 50 percent and BOM cost by more than $0.30 (USD).



Offering the industry's lowest parasitic losses, the Si85xx current sensors enable designers to maximize system efficiency and meet aggressive power budgets for green energy standards. The devices' low resistance (<1.3 milliohms) and small parasitic inductance (<2 nH) result in more efficient power supplies that are easier and quicker to design.



Silicon Labs' ISOpro Si85xx isolated ac current sensors provide a space- and cost-saving alternative to traditional transformers and their associated external components, said Dave Bresemann, vice president of Silicon Laboratories. The new Si85xx current sensors also greatly improve system reliability. Based on mainstream CMOS process technology, the Si85xx devices require no hand winding or calibration at assembly unlike conventional mechanical transformers, which suffer from electrical and mechanical variations that reduce reliability and cause manufacturing headaches.



To ease the design process, the Si85xx ac sensor family is supported by a complete set of development tools including the Si85xx-EVB evaluation board and the OPENLPPOL-EVB open-loop point-of-load reference design.