The AM08XX and AM18XX families of real-time clock (RTC) chips from Ambiq Micro Inc., Westlake Hills, TX, have a typical active current from <20 nA to 55 nA. The devices provide onchip oscillators; full RTC functionality including battery backup, programmable counters, and programmable alarms for timer and watchdog functions; and a 1.8–4.1 V voltage range for serial communication. The AM18XX family couples ultra-low-power RTC functions with advanced power management capabilities; an onchip Power Switch and System Sleep Manager let the devices act as supervisory elements in a host microcontroller-based system.