Octal high side switches combine galvanic isolation with energy efficiency
Eight-channel octal high side switches, the ISO808, ISO808A, ISO808-1 and ISO808A-1 have been introduced by STMicroelectronics to protect industrial loads.
The switches combine galvanic isolation for robustness, RDS(on) below 260mOhm for energy efficiency and protection and diagnostics for reliability and fault recovery, said the company.
The four eight-channel switches drive all types of industrial loads, i.e., capacitive, resistive, and inductive, with one side connected to ground. Typical uses are in programmable logic controllers (PLC), industrial PCs, and computer numerical control (CNC) machines, especially where isolation is needed to increase protection for sensitive smart factory electronics, said STMicroelectronics.
The ISO808 and ISO808A have a current limit of 0.7A, while the ISO808-1, ISO808A-1 have a limit of 1A. The ISO808 and ISO808-1 provide a separate input pin for each channel and allow either direct control or synchronous operation driving all outputs simultaneously. The ISO808A and ISO808A-1 have a serial SPI (serial peripheral interface) input and feature an open-drain power-good (Pgood) indicator to aid system management. All switches have a dedicated fault indicator pin.
Overload protection operates independently on each channel, so non-over-loaded channels can continue operating normally. Any over-loaded channels are turned off and automatically restarted to permit rapid recovery with minimal host intervention. The channel is shut down again if the fault remains, which is detected by monitoring channel and case temperatures. Other features include ground disconnection protection, reverse-polarity protection, short-circuit protection, thermal case protection, and under-voltage shutdown for both the control-side (VDD) and process-side (VCC) power rails. Communications across the isolation barrier are by RF (radio frequency) which maximises noise immunity. Internal logic reports any data errors and a watchdog ensures the process-stage outputs are safe if the control-side supply voltage is missing.
The switches help ensure industrial applications meet applicable international standards including IEC 61000 specifications for electrostatic discharge (ESD), electrical transients, and power-frequency magnetic-field immunity. They comply with UL1577 and UL508 isolation specifications and VDE 0844-11 safety limits.
The ISO808 family are pin-compatible with other popular switches, confirmed ST. They can also benefit from a development ecosystem, including four X-NUCLEO industrial digital-output expansion cards (X-NUCLEO-OUT11A1, X-NUCLEO-OUT12A1, X-NUCLEO-OUT13A1, and X-NUCLEO-OUT14A1) for STM32 Nucleo development boards accelerate evaluation, while the graphical application, STSW-IFAPGUI, eases configuration and control.
The ISO808 family is available now, housed in a PowerSO36 package.
