# Backup Domain Clock¶

group group_sysclk_clk_bak

The backup domain clock drives the RTC (Real-Time Clock).

This clock has two possible source clocks: WCO or the Low-Frequency Clock. In turn the low frequency clock is sourced by ILO, PILO, or WCO. Typically the ILO is not suitable as an RTC source, because of its low accuracy. However the ILO does operate in hibernate mode and may be used as an alternative to the WCO with a tradeoff in precision.