Embedded microcontroller (MCU) based systems have historically relied on a low frequency 32.768 kHz quartz resonator driven oscillator for time keeping and failure recovery functions. TempFlat™ MEMS SiT153x oscillators and SiT155x temperature compensated oscillators (TCXOs) are a new generation of smaller footprint 32.768 kHz devices that offer a cost effective, more reliable, improved frequency stability alternative to quartz-based 32.768 kHz oscillators. This application note gives an overview of on-chip 32 kHz oscillator modes used in low power MCUs and the different drive settings supported by the SiT15xx families. The SiT15xx devices feature NanoDrive™, a factory programmable output voltage swing to optimize power and connectivity to existing oscillator sustaining circuits. This document lists valid combinations of SiT15xx output drive VOH/VOL settings and the associated part number for specific MCUs.