This is a 32768Hz crystal oscillator specifically designed for ultra-low power application. The sole power supply is 3.3V, but it can be as low as 1.6V while the oscillator can still function properly. The oscillator works in parallel resonant mode of the crystal. When a 32768Hz quartz crystal is connected to pins XIN32K and XOUT32K, the oscillator will output 32KHz and 1Hz square waves, with the average current less than 2uA.