260- $\mu$ W DCO With Constant Current Over PVT Variations Using FLL and Adjustable LDO

In this brief, the design of an ultralow power digitally controlled oscillator (DCO) for Bluetooth low-energy applications is proposed. The DCO core is designed to operate in the subthreshold region. The DCO power consumption is reduced mainly by maintaining the constant current over process, voltage, and temperature (PVT) variations in the oscillator core via an adjustable low-dropout (LDO) regul...