This application note describes some of the most common issues related to ST's family of serial real-time clocks (RTCs), including crystal layout, oscillator circuit, undershoot protection, etc.
This document serves as a compilation of common issues and design considerations for STMicroelectronics' M41 family of serial real-time clocks (RTCs). It covers essential topics ranging from physical layout requirements for crystals to proper software initialization sequences upon power-up. The guide aims to help engineers understand the subtleties of these devices to ensure reliable timekeeping.
No, ST's real-time clocks have built-in load capacitors, so external load capacitors or resistors are not needed.
The crystal must be a 32,768 Hz watch crystal.
Most ST real-time clocks specify a minimum Vcc of -0.3 V.