Digital Isolator from STMicroelectronics Boosts Performance and Reliability Using New Thick-Oxide Galvanic Isolation Technology

STMicroelectronics has begun volume production of the STISO621 dual-channel digital isolator, launching a new series of high-performance ICs for industrial applications and general optocoupler replacement.

The STISO621 transfers data between two isolated domains at up to 100Mbit/s, with pulse distortion below 3ns, leveraging ST’s 6kV thick-oxide galvanic-isolation technology. With two independent unidirectional channels, the device performs as a UART interface handling data in both directions. 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 (CMTI) of 65kV/µs protects the low-voltage side against high switching transients in harsh environments.

The STISO621 is suited to a wide range of industrial and consumer applications in power supplies, motor drives, meters, inverters, battery monitors, appliances, fieldbus isolators, size-critical multichannel isolation adapters, and general isolation throughout industrial-automation systems. The design is tested in accordance with VDE0884-10 and UL 1577, the specifications typically applied to isolation devices for high-voltage applications.

The EVALSTISO62XV1 product evaluation board is available to help accelerate design completion in multiple applications. The EVALSTPM-3PHISO reference design, specifically designed for three-phase isolated metering-systems use cases, is also available. It combines the STISO621 to separate high voltage domains with ST’s high-accuracy STPMS2 metering front-end IC and specific firmware running on an STM32 microcontroller to compute three-phase metrology and power-quality data.

With a maximum working isolation voltage (VIOWM) of 1200Vpeak, and high impulse-withstand voltage (VIOTM), galvanic insulation integrity is maintained over time and during any system faults. Two package variants are offered. In the SO8 narrow-body package with 4mm creepage and clearance, the STISO621 has VIOTM of 4800V. The STISO621W in the SO8 wide-body package with 8mm creepage and clearance has VIOTM of 6000V. High performance level is guaranteed from -40°C to 125°C temperature range.

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