EYE ON NPI - XP Power PBT02F Series 2W DC/DC Converters w/ SMD Footprint

Adafruit Industries

This week's EYE ON NPI is all about isolation (https://www.youtube.com/watch?v=6x-Nl3_L1pA), it's the XP Power PBT02F Series 2 W DC/DC Converters with SMD Footprint (https://www.digikey.com/en/products/base-product/xp-power/1470/PBT02F/737947)! A compact and easy way to add power isolation to your design without having to muck around with transformer matching and isolation testing. We've covered lots of power supply solutions on EYE ON NPI (https://blog.adafruit.com/tag/eye-on-npi/) including bucks (https://www.youtube.com/watch?v=sEoM5vUjwwI), boosts (https://www.youtube.com/watch?v=2NJzL0jCmfU) and even buck-boosts (https://blog.adafruit.com/2024/08/09/eye-on-npi-analog-devices-max77859-buck-boost-converter-eyeonnpi-digikey-digikey-adi_news/) but we haven't yet covered an isolating chip/module. However, they're so useful when you want to make sure that your electronics are not connected directly to a power supply or Earth ground. This could be for safety reasons: you want to make sure that there is no way for a high voltage from the input to somehow make its way into the output. Or it's used to make sure that a DAQ doesn't have a ground loop. Or maybe you're measuring/controlling a high voltage system from a low voltage - isolating power and data is essential. And speaking of, we often do have to isolate both data and power! Remember that digital and analog signals are always ground referenced so it's no good to have just data or just power isolation: you need them both! Data isolation is a lot easier than power though: you can use optical a-la your common optoisolator (https://www.digikey.com/en/products/category/optocouplers-optoisolators/2058), capacitive (https://www.adafruit.com/product/4903), or even chip scale micro-transformers (https://blog.adafruit.com/2024/03/14/eye-on-npi-analog-devices-adum1252-3-bidirectional-i%C2%B2c-isolators-eyeonnpi-digikey-digikey-adi_news-adafruit/). We have more flexibility because we only have to transfer signal, not actual power: all of those techniques assume that the 'opposite side' of the converter has isolated power ready to go. But that means that we have to do the hard part of actually transferring power over an air-gap. Now if you happen to be isolating AC power, say from 120V or 240V AC mains, this is super easy: just stick a transformer on there (https://en.wikipedia.org/wiki/Transformer) and you'll magically get isolation with the benefit of also being about to step up or down the voltage. But transformers don't work with DC, so what engineers have to do is create a buck/boost converter that uses a transformer instead of a plain inductor, thus creating the isolated flyback (https://www.xppower.com/storage/documents/technical-articles/PSUTopologies.pdf), a low cost way to transfer a couple watts. The XP Power PBT02F Series (https://www.digikey.com/short/5nh10cq0) come in a few variants, thanks to the built-in buck/boost converter topology. You can input voltages from 3 to 24VDC and get 3 to 15V out. There are even versions with 'split' dual outputs: a nice bonus from having a mid-tapped transformer (https://en.wikipedia.org/wiki/Center_tap) that can give you a centered ground reference. And one of my favorite things about it is that the whole transformer-DC/DC comes in a mini sealed pick-and-placeable package that is only 0.5" x 0.42" x 0.35", about the size of a coffee bean! Note the dual-output version is a little chunkier at 0.6" long - maybe like a chocolate-covered coffee bean. If you need a ultra-compact isolating power supply solution with buck or boost capabilities, the XP Power PBT02F Series (https://www.digikey.com/short/5nh10cq0) is going to satisfy your requirements! Available in a variety of options (https://www.digikey.com/en/products/base-product/xp-power/1470/PBT02F/737947), we're going to check out the PBT02F05S05 5V in/out (https://www.digikey.com/short/5nh10cq0) for our next USB isolation project. Best of all, it's in stock right now for immediate shipment from DigiKey! Order today and you will be designing and testing your power supply by tomorrow morning.