#prototypeboard

We designed this split +12/-12 power supply board based on the TPS65131 (https://www.digikey.com/en/products/detail/texas-instruments/TPS65131RGER/1672464) a few months ago, but it languished while we worked on some other projects. We had an issue where the negative power rail was unstable. Thankfully, we found a thread that suggested slowing down the VNEG feedback loop (https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/628380/tps65131-q1-abnormal-operation-of-tps65131-q1-s-vneg) with a 51k resistor. We hand-soldered that in, and it worked nicely. Then, the other fix was to flip around the trimmers so the turn direction matched the expected behavior. This should be good to book a second prototype, and then it can go into the shop.

The ADI DS3231 - previously known as Maxim, previously previously known as Dallas Semi - is a high precision Real Time Clock - its one of the best out there thanks to it's internal temperature compensated crystal. but its kinda old, and ADI has done a refresh on the chip while keeping it software/firmware compatible. The MAX31328 https://www.digikey.com/short/5jff8p90 is a different, smaller package, probably uses a modern-er process too. We covered this family on EYE ON NPI about a year ago https://blog.adafruit.com/2022/05/26/eye-on-npi-analog-devices-maxim-max31329-real-time-clock-rtc-eyeonnpi-adi_news-digikey-adafruit/ and parts we booked back then finally appeared so we can design a prototype board! here it is in our STEMMA QT format - on the back is a coin cell holder to keep time for up to 7 years.

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