An oscillator includes first, second, and third current sources, a resistor having first and second terminals, first and second capacitors each having first and second terminals, a switch circuit through which each of the current sources is connectable to the first terminal of one of the resistor and the two capacitors to supply current thereto, a comparator, and switch controller configured to generate control signals for the switch circuit and an oscillation output signal for each of multiple periods based on an output signal from the comparator. During one of the periods, the switch circuit is controlled to connect the first current source to the first terminal of the first capacitor, the second current source to the first terminal of the resistor, the first terminal of the resistor to a first input of the comparator, and the first terminal of the first capacitor to a second input of the comparator.

A circuit includes a first power node having a first voltage level, a second power node having a second voltage level different from the first voltage level, a reference node having a reference voltage level, a master latch that outputs a first bit based on a received bit, a slave latch that outputs a second bit based on the first bit and an output bit based on a selected one of the first bit or a third bit, a first level shifter that outputs the third bit based on a complementary bit pair, and a retention latch including a second level shifter and a pair of inverters that outputs the complementary bit pair based on the second bit. The slave latch and the first level shifter are coupled between the first power and reference nodes, and the retention latch is coupled between the second power and reference nodes.