EYE on NPI - Abracon Real-Time Clock with Integrated 32.768 kHz Crystal Oscillator

This week's EYE ON NPI is tick tock o'clock, it's the Abracon Real-Time Clock with Integrated 32.768 kHz Crystal Oscillator (https://www.digikey.com/en/product-highlight/a/abracon/real-time-clock-with-integrated-32-768-khz-crystal-oscillator). It's a tiny and affordable all-in-one RTC that has everything ya want, and nothin' ya don't. With it's compact package size, it's half the BOM size of what most RTC's need, and has a high quality Abracon crystal (https://www.digikey.com/en/supplier-centers/abracon) already included! We've been using Abracon (https://www.digikey.com/en/supplier-centers/abracon) crystals and oscillators in our designs for decades - for example a 12.288 MHz Crystal (https://www.digikey.com/short/w2qvtnbr) adorns our VS1053 breakout board (https://www.adafruit.com/product/1381). That's not the only thing they're good at, but it's the name recognition they've got as a trusted supplier of quality, affordable crystals and oscillators. So it was not surprising for us to learn that they now have an integrated-crystal real time clock chip for sale. Real time clock chips are specialty low-cost chips that keep track of 'real time' (e.g. the month, day, year, hour, minute, second) so that the rest of the system can go into shutdown mode or lose power, without losing track of time. They also often have alarms so that the system can reboot out of deep sleep to perform some task at an assigned delay or timestamp. As you might expect, the important characteristics to look for in an RTC are accuracy - how close their internal timekeeping is to true time - and power draw - how long they can run off the secondary power source such as a super-cap or coin cell battery (https://www.digikey.com/en/products/detail/panasonic-energy/CR-1025-BN/269738). There's other characteristics that you may care about: the voltage range they can power off of, whether they support a secondary battery backup with auto-switchover, and of course the interface and capabilities like alarms The AB-RTC-XB-32.768KHZ-2-T3 (https://www.digikey.com/short/tp4tjzqz) has many of the things we like to look for in an RTC. First, is a standard I2C interface - most RTCs are, and this makes it easy to add to any microcontroller or microcomputer. Second is a wide operating voltage range for power and logic: 1.2V to 5.5V with both a power and IO power pad! That means it's great even for low voltage cores or 5V Arduino-compatibles, and you can have separate voltages if desired. Alongside those two pins there's also a separate VBat pin for backup battery with auto-switchover. That means when the main power cuts off, say because USB got unplugged, or the main Lipoly battery is drained, we'll switch over to a coin cell or super-cap. Of course, the big feature of this RTC is the built-in crystal. By integrating directly, they're able to have an SMT chip with no external crystal in a 3.2 x 2.5mm package - the same size as most crystals! According to the datasheet, the crystal has a 5 ±23ppm frequency stability at room temp 25℃. That translates to 28 ppm max: 86,400 × (28/1,000,000) = 2.42 seconds gain/loss per day. At the typical 'best case' of 5ppm, its 86,400 × (5/1,000,000) = 0.432 seconds per day. That's in-line with most RTC crystal specifications, although it wouldn't be considered 'high precision' since its not temperature compensated. Temp compensation is much more complex and expected, and most RTCs will get auto-sync from the controller via WiFi/BT/GPS to apply correction every day~month to get them back on track. If you need a compact real time clock with a flexible power supply setup and Abracon-quality crystal, the AB-RTC-XB-32.768KHZ-2-T3 (https://www.digikey.com/short/tp4tjzqz) is an excellent new product offering that's available and in stock at DigiKey right now! Order today and before your morning alarm goes off you'll have this chip in hand and ready to integrate into your next product design.