STMicroelectronics releases current-isolated high-side switches for diagnostic control and protection of industrial loads

     STMicroelectronics announces a series of eight-way output high-side switches. The new product features current isolation and protection diagnostics with on-resistance RDS(on) of less than 260 Mω, improving application resistance, energy efficiency, reliability and failure resilience. The newly released eight-way output switches ISO808, ISO808A, ISO808-1 and ISO808A-1 drive all types of single-side grounded industrial loads, such as capacitive, resistive and inductive loads. Typical use cases are programmable logic controllers (PLCS), industrial PCS, and computer numerical control (CNC) machines, especially sensitive electronics in smart factories that need to isolate currents for enhanced protection.

     ISO808 and ISO808A are limited to 0.7A, while ISO808-1 and ISO808A-1 are limited to 1A. Each output of ISO808 and ISO808-1 has a separate input pin that can be directly controlled or synchronised to switch operation and drive all output pins simultaneously. ISO808A and ISO808A-1 have serial SPI input pins and open Drain Power Normal (Pgood) indicating pins for easy system management. All products have a dedicated fault indication pin.

     Each output has a separate overload protection mechanism, so that channels that are not overloaded can continue to operate normally. The protection mechanism detects overload events by monitoring the temperature of the channel and the temperature of the enclosure. When the overload is detected, the channel is closed, and then the channel is automatically reopened and quickly restored to the normal state, minimizing the involvement of the main controller. If the fault persists, the channel is closed again.

     The control side (VDD) and processing side (VCC) power rails have ground break protection, reverse polarity protection, short circuit protection, housing thermal protection, and undervoltage shut-off functions. Both sides of the barrier transmit data via radio frequency to maximize noise resistance. The internal logic circuit load reports any data errors, and if the control side power supply voltage is lost, the watchdog ensures that the processing level output power is safe.

     The performance and characteristics of these switches help industrial applications comply with applicable international standards, including electrostatic discharge (ESD), electrical transients and power frequency field immunity of IEC 61000 specifications, compliance with UL1577 and UL508 isolation specifications, and VDE 0844-11 safety restrictions. In addition to compatibility with other brands of switch pins that are hot on the market, ST's ISO808 series has additional advantages, such as lower on-resistance for RDS(on) and power good pins for SPI input products.

     The ISO808 family has a huge development ecosystem and has many advantages over other branded products. Four X-NUCLEO industrial digital output expansion boards (X-Nucleo-Out11A1, -OUT12A1, -OUT13A1, and -OUT14A1) in conjunction with the STM32 Nucleo development board expedite device suitability evaluation. The graphical interface application software STSW-IFAPGUI simplifies device configuration and control.