ST adds galvanically isolated high-side switches
Robust octal high-side switches feature diagnostics and protection for reliability and fault recovery
STMicroelectronics has launched a family of octal high-side switches that combine galvanic isolation for robustness, RDS(on) below 260mΩ for energy efficiency, and protection and diagnostics for reliability and fault recovery.
The 8-channel switches, ISO808, ISO808A, ISO808-1, and ISO808A-1, drive all types of industrial loads - 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.
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 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-overloaded channels can continue operating normally. Any overloaded 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.
There is also 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, 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 performance and features of these 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.
While pin-compatible with other popular switches, ST’s ISO808 family delivers the extra benefits of lower RDS(on) and the power-good pin of the SPI-input variants.
An extensive development ecosystem supports the ISO808 family, presenting an additional advantage over alternative devices. Four X-NUCLEO industrial digital-output expansion cards (X-NUCLEO-OUT11A1, -OUT12A1, -OUT13A1, and -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, priced from $5.56 for orders of 1000 pieces.
