New Industry Products

STMicroelectronics Begins Volume Production of Digital Isolator Featuring Galvanic Isolation

April 28, 2021 by Gary Elinoff

The STIS0621 provides 6kV of galvanic isolation and features two independent unidirectional channels

The STISO621 from STMicroelectronics (ST) transfers data at speeds up to 100 Mbits per second, serving as a UART interface by transmitting unclocked information in both directions

The STIS0621. Image courtesy of ST
The STIS0621. Image courtesy of ST


The STIS0621 employs ST’s thick oxide galvanic isolation technology. It features Schmitt-trigger inputs on each channel, affecting a high level of noise immunity. The supply voltages feeding each of the two directional channels are independent of each other, which allows for level translation between 3.3V and 5.5V circuitry. 


What is Galvanic Isolation Technology?

Galvanic isolation allows power or information to pass between two electrical circuits, while maintaining electrical isolation between the circuits. 

The most common example is a transformer, with current changes in the primary windings causing analogous signals to appear in the secondary. 

Another example is the opto-isolator, where digital pulses containing information are used to turn on and turn off a LED. The light pulses are picked up by a light sensitive transistor, which generates electrical impulses that reproduce the information originally transmitted by the LED

Galvanic isolation blocks electrical surges on one side of the barrier from affecting circuitry on the other side. And, most importantly, in neither case is it required that the two circuits share a common ground


Key Isolation Facts for the STIS0621

  • The isolator features a typical common-mode transient immunity (CMTI) of 65kV/µs, which serves to protect against high switching transients in harsh environments. 
  • It also offers a maximum peak working isolation voltage (VIOWM) of 1200 volts.
  • The devices come two packages with different high impulse-withstand voltages (VIOTM) 
  • SO8-N (narrow) package devices offer 4mm creepage and clearance, and a VIOTM of 4800V. 
  • SO8-W (wide) units feature 8mm creepage and clearance has VIOTM of 6000V 


Important Electrical Specifications

  • The recommended supply voltage range is from 3 to 5.5 volts, and the device’s ON threshold is 2.8 volts. 
  • The maximum data rate is 100 Mbps
  • The unit typically draws 3.65 mA at 10 Mbps. 
  • At 100 Mbps, with a capacitive load of 20 pF, the typical current drawn will be 18 mA.
  • Output impedance is 50Ω
  • Pulse width distortion over the full temperature range is a maximum of 3ns



  • Replacing slow, troublesome optocouplers
  • Industrial bus isolation
  • Battery monitors
  • Motor drives
  • Multichannel isolation in size-critical applications


Physical Considerations

The units operate over a -40 to 125°C temperature range. 

Maximum dimensions, including gull wings are:

  • SO8-W: 6.06 by 10.52 mm
  • SO8-N: 5.00 by 6.20 mm


Regulatory and Safety

The device is tested in accordance to:

  • VDE0884-10
  • UL 1577 


Getting to Market Faster

The EVALSTISO62XV1 evaluation board enables designers to familiarize themselves with the STIS0621. The board comes complete with both the narrow and wide packaged versions of the STIS0621, which the users can themselves mount. 

The EVALSTISO62XV1. Image courtesy of ST
The EVALSTISO62XV1. Image courtesy of ST


It will enable engineers to quicken the pace of the design process across a range of applications.