All-digital phase locked loop using switched capacitor voltage doubler

Abstract

An all-digital phase locked loop (ADPLL) receives an analog input supply voltage which is utilized to operate analog circuitry within the ADPLL. The ADPLL of the present disclosure scales this analog input supply voltage to provide a digital input supply voltage which is utilized to operate digital circuitry within the ADPLL. The analog circuitry includes a time-to-digital converter (TDC) to measure phase errors within the ADPLL. The TDC can be characterized as having a resolution of the TDC which is dependent, at least in part, upon the digital input supply voltage. In some situations, process, voltage, and/or temperature (PVT) variations within the ADPLL can cause the digital input supply voltage to fluctuate, which in turn, can cause fluctuations in the resolution of the TDC. These fluctuations in the resolution of the TDC can cause in-band phase noise of the ADPLL to vary across the PVT variations. The digital circuitry regulates the digital input supply voltage to stabilize the resolution of the TDC across the PVT variations. This stabilization of the resolution of the TDC can cause the ADPLL to maintain a fixed in-band phase noise across the PVT variations.