Silicon Labs introduces the industry's first high-speed multi-channel PLC input isolator

     SiliconLabs introduces the industry's first high-speed, multi-channel digital isolator designed to meet the needs of programmable logic controller (PLC) applications. The new Si838x PLC isolator family offers an unmatched combination of features: high speed channels (up to 2Mbps), high channel integration (up to 8 channels per device), bipolar input flexibility, high anti-jamming and a 2.5kVRMS secure isolation rating. The Si838x series provides specially built solutions for PLC applications including industrial I/O modules, computer numerical control (CNC) machines and servo motor control. In addition, the Si838x isolator is ideal for process automation controllers (PACs) in distributed process control systems.

     PLCS are widely deployed in harsh factory floor environments, so they must be both reliable and compact. Many PLCS are designed to scale up to 128 channels and have multiple high-speed inputs. Although optocouplers have provided the default isolation solution for decades, they have also presented PLC designers with great challenges. Due to the lack of high-speed capabilities, optocouplers cannot meet high performance PLC applications, such as servo motor control. Optocouplers also lack high noise suppression and their performance degrades over time and temperature, thus posing reliability risks in high-temperature industrial applications. For the first time, the Si838x family fully overcomes these challenges, offering a flexible, high-speed, multichannel bipolar isolation solution in a compact QSOP package that offers longer service life and increased reliability compared to optocoupler-based solutions.

     The Silicon Labs Si838x isolator is a highly integrated single-chip device that provides an 8-channel 24V digital interface. This high level of integration significantly saves on bill of material (BOM) costs and board area for PLC designs. By connecting 16 Si838x isolators with a "daisy chaining" in the system design, developers can leverage a single serial peripheral interface (SPI) on the system's embedded processor to create PLC designs that support up to 128 channels.

     The controller interface can be 8 parallel channels or 1 4-wire SPI. Developers can configure SPI to achieve instant programming for noisy signal de-jaking and Daisy chains that support high channel density PLC designs. An optional de-jitter filter can be pre-programmed in a parallel configuration or directly programmed in a serial output configuration.

     With Silicon Labs' pioneering CMOs-based LED simulator technology, the Si838x isolator has a flexible bipolar input capability that allows developers to choose between Sinking or Sourcing inputs. The LED emulator input circuit supports up to eight Sinking or Sourcing inputs in a single isolator device, and no power is required on the field side. The output interface connected to the controller supports 2.25V low-power operation.

     The Si838x isolator supports high 1MHz(2Mbps) rates, which are necessary for servo motor control applications. The isolators also provide optimal noise suppression in high-speed channels (typical 50 kV/µs CMTI), enhancing system reliability.

     Ross Sabolcik, vice president of Power Products at Silicon Labs, said: "Silicon Labs' Si838x family of products addresses several unique challenges in PLC design by providing compact, multi-channel, high-speed digital isolation solutions. PLC developers can now easily migrate their optocoupler-based designs to state-of-the-art digital isolation technologies that provide higher performance, greater design flexibility, higher channel density, and long-term reliability."