Silicon Labs’ Isolated Smart Switches Work in Harsh Industrial Environments

September 4, 2019 Alix Paultre

Silicon Labs introduced the Si834x family of compact and robust isolated smart switches, designed to drive resistive and inductive loads such as solenoids, relays and lamps in harsh industrial environments. Each switch is galvanically isolated for safety using CMOS-based isolation technology, offering advantages like a common-mode transient immunity (CMTI) of more than 100 kV/μs.

Features include high-side and low-side switch options, anon-resistance of 145 mΩ RON, up to 700 mA of continuous current compliant with the IEC 61131-2 standard, comprehensive protection and diagnostic reporting, and advanced configuration, monitoring and control for industrial automation systems. The switch logic interface can be as simple as four low-power CMOS digital inputs or as rich and flexible as a full serial peripheral interface (SPI) capable of controlling up to 128 channels with four MCU pins.

“The new Si834x isolated smart switch family embodies three generations of Silicon Labs’ isolation innovation for industrial automation,” said Brian Mirkin, Vice President and General Manager of Silicon Labs’ power products. “The Si834x family expands our broad isolator portfolio, complementing our PLC input isolators and isolated FET drivers to provide a complete solution. The Si834x switches outperform opto-isolators, power FETs and other competing options by offering a fully integrated 24 V digital output solution with best-in-class switch protection, flexible configuration and comprehensive diagnostic feedback.”

Each switch can detect an open-circuit condition and is protected against over-current, over-voltage from demagnetization (inductive kick or flyback voltage), and over-temperature conditions. A multi-voltage smart clamp handles demagnetization energy, and overcurrent protection includes an inrush current mode to drive challenging loads. While other solutions entering into a fault state may shut down, Si834x switches can continue operation in a constrained but functional state with reduced channel performance.

Additional features include a logic interface with eight separate diagnostic reports, configured, monitored, and cleared through SPI or exposed on active-low, open-drain indicator pins for easy access. Diagnostic communication is independent of the switch control signals across the isolation barrier, with separate isolation channels and constant fault monitoring, providing system operators with detailed information about how the switches and their loads are behaving on the other side of the isolation barrier.

Available now in a 9 mm x 9 mm DFN-32 package with an exposed center pad (ePAD), the Si834x4x switches with a parallel interface are priced at $1.90 each (USD) in 100,000-unit quantities. The Si834x8x switches supporting SPI are priced at $2.09 each in 100,000-unit quantities. To simplify development and accelerate time to market, Silicon Labs offers Si834x evaluation kits with either a parallel or SPI interface and sinking/sourcing output options.

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