EYE on NPI: Skyworks Si3404 and Si3406x Power over Ethernet (PoE) Powered Device Chips @digikey
33This week's EYE ON NPI is an EYE in the SKY, as we're featuring our first NPI from Skyworks: the Skyworks Si3404 and Si3406x Power over Ethernet [PoE] Powered Device Chips (https://www.digikey.com/en/product-highlight/s/silicon-laboratories/si3404-and-si3406x-power-over-ethernet-powered-device-chips). PoE is a standard, supported by many Ethernet hubs and switches (https://www.tp-link.com/us/solution/poe/) that allows a device connected to the hub to request +48V power over some of the Ethernet lines in Cat-5 cabling.
Since many devices need Ethernet for speed and reliability - cameras, phone systems, printers, standalone monitors, and door entry systems, for example - you only need a single cable. These chips, originally from Silicon Labs and now made and sold by Skyworks, allow product designers to quickly add PoE support to their Ethernet products, saving space, complexity and wiring because a separate power supply is no longer needed.e
First up, if you're wondering: "wow Skyworks, where have I seen that name before?" That's right! It was the California fabrication facility (https://en.wikipedia.org/wiki/Such_Great_Heights#Music_video) where The Postal Service's Such Great Heights video was shot (https://www.youtube.com/watch?v=0wrsZog8qXg). The original video even featured the Skyworks logos on the chips - now it's blurred out. But that's a great excuse for us to mention that there's a Postal Service/Death Cab 20th Anniversary Tour this fall and we are definitely getting tickets (https://giveuptransatlanticismtour.com/).
But back to PoE chips! We watched a discussion video (https://www.youtube.com/watch?v=tEhbVpYFvk0) about the history of this chip line, we were struck by the observation that the reason PoE is so popular for office buildings is that it's very disruptive and expensive to get electricians to run power outlets everywhere. But running Ethernet can be done by the IT department because the voltages are so low that no special licensing or permitting is needed. Ethernet can be run behind drywall, around door frames, or under drop floors without worrying about electrocution or fire hazards. And you don't have to worry about DC plug adapters or voltage mismatches.
The Si3404 can provide up to 13W (https://www.digikey.com/short/49dqqh9m), the Si3406 can do 25W (https://www.digikey.com/short/35jn99tc) but are otherwise very similar. Other than a few passives and full-wave bridge rectifiers, you only need the flyback inductor-transformer (https://www.digikey.com/en/products/filter/switching-converter-smps-transformers/168) - for isolated setups, it's a little more complicated. The Si3404 can also perform as a non-isolated buck converter for very small and low cost designs. The output voltage is set by a simple feedback resistor divider. Designs are compact, less than 1 square inch, for most use cases.
Both the Skyworks Si3404 (https://www.digikey.com/short/49dqqh9m) and Si3406 (https://www.digikey.com/short/35jn99tc) are in stock right now at Digi-Key for immediate shipment. There are also eval boards (https://www.digikey.com/en/product-highlight/s/silicon-laboratories/si3404-and-si3406x-power-over-ethernet-powered-device-chips) that come with buck/flyback/isolated setups so you can test them as replacements for your current power supply to make sure which schematic you'll follow. Order them today for immediate delivery - through the Postal Service or whatever your favorite carrier may be - and you'll be making your IoT designs easy-to-power by tomorrow afternoon!