EYE on NPI - Analog Devices ADuM1252/3 Bidirectional I²C Isolators

Adafruit Industries

This week's EYE ON NPI will galvanize your next design, with robust galvanic isolation specifically for I2C devices: we're highlighting the Analog Devices ADuM1252/3 Bidirectional I²C Isolators (https://www.digikey.com/en/product-highlight/a/analog-devices/adum1252-bidirectional-i2c-isolator). They are available in two flavors: as the unidirectional ADuM1253 (https://www.digikey.com/short/0w8fq3w5) and bi-directional ADuM1252 (https://www.digikey.com/short/r4j3tcrf). These little SOIC chips provide trustworthy isolation up to a shocking ±10 kV surge, with pending safety and regulatory approvals, so you can feel confident that your design is created as safe as possible. Digital isolation (https://www.analog.com/en/product-category/isolation.html) is essential when dealing with medical, industrial or robotic designs. For industrial/robotic applications, the motors are very noisy and you want to make sure that there is no direct path for that electrical noise to your delicate sensors or microcontrollers. With medical cases, engineers are often tasked with measuring very fine sensors, with uV signals, and providing repeatable data that is used for life-or-death decisions, while also making sure that the 'DUT' is never exposed to dangerous voltages all in an environment with tons of other equipment, some of which may be misbehaving...that's a lot of pressure! The ADuM1252/3 is specifically designed for isolation of I2C signals: you can't just use 'any' isolator because I2C is a bi-directional data protocol that uses pull-ups on open-drain data and clock lines to communicate from controller and peripheral. The ADuM1252 (https://www.digikey.com/short/r4j3tcrf) has bi-directionality on both SDA and SCL, useful for 'multi-controller' modes or when clock stretching is used. The ADuM1253 (https://www.digikey.com/short/0w8fq3w5) has unidirectional SCL for most common I2C devices, and is a little less expensive. The ADI iCoupler technology uses 'galvanic' isolation, that's not the same as optoisolation! According to ADI, you'll get much better data-rate performance and isolation with galvanic compared to optoisolation. Also, lower power since you don't have to turn on/off an LED. Plus you can also use iCoupler for power transfer, which optoisolation cannot do. (https://www.analog.com/media/en/technical-documentation/frequently-asked-questions/icoupler_faq.pdf) The way iCoupler works is by creating a tiny transformer (https://en.wikipedia.org/wiki/Transformer) with two sets of metal coils, separated by an isolating polyamide layer. For data transfer, little coils are used and for power transfer, bigger coils can handle a couple mA! Of course, if we're using a transformer, you know that DC signals cannot be passed through, only AC; and data has a DC component plus isn't a sine wave. That means that there's also a data-to-AC codec on board that will turn I2C signals to AC, then back to I2C. All this is managed transparently so you don't have to worry about it, just treat it as a single I2C bus. There's also a couple nice extras that are helpful if you're trying to make I2C more fault-tolerant. Pre-charge circuitry and 'stuck' detection allow hot-swapping, either purposeful or accidental. The two isolated sides are not connected together until the Side2 half is in a neutral-bus condition. Since each side is separate, you can also use the ADuM1252/3 (https://www.digikey.com/short/1vbn4hcb) for level shifting: either half can be between 1.7 and 5.5V power and logic. With the fast iCoupler codec, you can get up to 2 MHz clock rate for fast I2C data transfer. If you need iCouplers for other protocols like USB or SPI - Analog devices has those available as well, each version is tuned for the usage so you get the best performance. If you need high performance galvanic isolation for your next I2C design, the Analog Devices ADuM1252/3 Bidirectional I²C Isolators (https://www.digikey.com/en/product-highlight/a/analog-devices/adum1252-bidirectional-i2c-isolator) will do an excellent job at creating a code-transparent galvanic barrier for up to 2 MHz bidirectional I2C communication. And best of all, both the unidirectional ADuM1253 (https://www.digikey.com/short/0w8fq3w5) and bidirectional ADuM1252 (https://www.digikey.com/short/r4j3tcrf) are stock at DigiKey right now for immediate shipment. Order today and you'll be gallivanting your way to iCoupler bliss by tomorrow afternoon. See the ADI video https://www.youtube.com/watch?v=4cH-ym9QJlQ