STMicroelectronics — STISO621 Dual-Channel Digital Isolator

STMicroelectronics STISO621 Dual-Channel Digital Isolator

Digital isolator offers reliable and high-performance alternative to an optocoupler

STMicroelectronics has begun volume production of the STISO621 dual-channel digital isolator IC, a high-performance replacement for optocouplers in industrial equipment.


The STISO621, which is based on new 6kV thick-oxide galvanic-isolation technology developed by ST, transfers data between two isolated domains at up to 100Mbits/s with pulse distortion of less than 3ns. Providing two independent unidirectional channels, the device performs as a UART data interface. Schmitt-trigger inputs to each channel ensure high noise immunity.


The supply voltages to the two mutually galvanically isolated sides of the STISO621 are independent of each other. Each has a wide voltage range, allowing level translation between 3.3V and 5.5V circuitry. Typical common-mode transient immunity of 65kV/µs protects the low-voltage side from high switching transients in harsh environments.


The design of the STISO621 is tested in accordance with the VDE 0884-10 and UL 1577 standards, the specifications which are typically applied to isolation devices for high-voltage applications.


Two package variants are offered. In the SO8 narrow-body package with 4mm creepage and clearance, the STISO621 offers maximum impulse-withstand voltage of 4,800V. In the STISO621W, supplied in an SO8 wide-body package with 8mm creepage and clearance, the withstand-voltage rating is 6,000V.


ST provides a reference design based on the STISO621, the EVALSTPM-3PHISO, for three-phase isolated metering systems. This design combines the STISO621 to separate high-voltage domains with ST’s accurate STPMS2 metering front-end IC, together with firmware running on an STM32 microcontroller to compute three-phase metrology and power-quality data. ST also supplies a general-purpose evaluation board for the STISO621, the EVALSTISO62XV1.


  • 1,200V peak isolation voltage
  • Low power consumption
  • Operating-temperature range: -40°C to 125°C


  • Power supplies
  • Motor drives
  • Meters
  • Inverters
  • Battery monitors
  • Industrial appliances
  • Fieldbus isolators

Evaluation Board

Board Part Number: EVALSTISO62XV1

The STISO621 evaluation board features a dual-channel digital isolator operating from a supply voltage up to 5V and offering 6kV of galvanic isolation.

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