EYE ON NPI - STMicroelectronics' ST25 NFC Smart Tag Set

Adafruit Industries

This week's EYE ON NPI has some Nice Freakin' Chips - it's STMicroelectronics' NFC Smart Tag Set, (https://www.digikey.com/en/product-highlight/s/stmicroelectronics/st25-tag-bag-ut1-nfc-tag-set) with a cornucopia of labels, stickers, cards and tags that feature ST's Near Field Communication (NFC) chipsets, each with a matching antenna. This 18-piece kit is a great way to evaluate the different materials that NFC tags can be embedded in as well as verify that your NFC reader chipset works at the desired distances. NFC is built on top of the 'RFID' tags you're probably familiar with, unlike read-only RFID tags, NFC has bi-directional communication which means you can write values to the tags which makes them universal. For example, instead of having to manage a separate database that maps the 64-bit RFID value to a product SKU, the SKU itself can be written directly into the non-volatile memory on chip. Stuff like urls, timestamps, account balances, and sensor logs can go straight into the chip for anyone to access - or only for users with the correct password-unlock-code. NFC tags, stickers and cards are an upgrade from iButtons (https://www.analog.com/en/product-category/ibutton-products.html) -- less clunky, do not need to make electrical contact, magnetic stripe cards (https://en.wikipedia.org/wiki/Digital_card) -- can hold more information, are less flakey, don't delaminate or demagnetize, or barcodes (https://en.wikipedia.org/wiki/Barcode) -- need good light for optical reading, can be sluggish, very limited amount of data. Since NFC chips have bi-directional communication, plus built in encryption and writable memory, without any battery, they need to harvest energy from RF waves. That means that the the antenna is used for both data and energy and needs to be both tuned to the chip's internal capacitance as well as maximized in order to get the most E field possible (https://www.st.com/resource/en/application_note/an2866-how-to-design-a-1356-mhz-customized-antenna-for-st25-nfc--rfid-tags-stmicroelectronics.pdf). So, in general, the bigger the antenna the 'better' performance you'll get: shorter taps, less finicky alignment, and farther functionality. However - of course, you've got a bigger surface area for the tag. Here's the sizes that come in the ST NFC Smart Tag Set (https://www.digikey.com/short/rf5ddb3c): Three ST25TV02KC (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TV02KC-TFH3/18085938), 23 pF, tamper enabled label, 35 mm diameter Three ST25TN01K (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TN01K-AFH5/15775849), 50 pF, smart label, 30 mm diameter Three ST25TV02KC (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TV02KC-TFH3/18085938), 99 pF, smart label, 17 mm diameter Three ST25TV02KC (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TV02KC-TFH3/18085938), 23 pF, smart label, 50 mm x 50 mm Three ST25TV02KC (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TV02KC-TFH3/18085938), 23 pF, on-metal tag, 30 mm x 30 mm One ST25TV02KC (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TV02KC-TFH3/18085938), 23 pF, button tag, 22 mm diameter One ST25TN01K (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TN01K-AFH5/15775849), 50 pF, card, 85 mm x 54 mm One ST25TV02KC (https://www.digikey.com/en/products/detail/stmicroelectronics/ST25TV02KC-TFH3/18085938), 23 pF, NFC field detector with LED indicator, 85 mm x 54 mm A nifty feature we saw in the datasheet for the ST25 (https://www.st.com/en/nfc/st25tv-series-nfc-tags.html) is the "tamper detection" capability. Normally to make sure that the end-recipient can detect whether a box was opened in transit is to use a tamper detection sticker that tears when removed. Instead of needing two stickers, or even just relying on a human to properly detect the tampering, the ST25 chips have two extra contacts that can connect to a thin wire switch. When the sticker is moved the thin wire is broken and the chip will detect it. Since we can use encryption/authentication on the ST25, the tamper sticker tag can't be replaced. And, when using a digital logging system, it will automatically record the tamper without a person being able to fudge the reading. If you want to get started with integrating STMicroelectronics' ST25T NFC chips (https://www.digikey.com/en/products/filter/rfid-rf-access-monitoring-ics/880?s=N4IgjCBcoLQCxVAYygMwIYBsDOBTANCAG4B2aWehA9lANogDsAnGKyALqEAOALlCCAC%20woA) or tags into your product authentication/identification, access or inventory management, data logging, or asset tracking, then the NFC Smart Tag Set (https://www.digikey.com/short/rf5ddb3c) is a quick and easy way to get a wide range of stickers and cards to try out. Order today and DigiKey will pick, pack and post your order you'll have these tags in hand by tomorrow afternoon.