This paper proposes an ultra-low-voltage (ULV) fractional-N all-digital PLL (ADPLL) powered from a single 0.5-V supply. While its digitally controlled oscillator (DCO) runs directly at 0.5 V, an internal switched-capacitor dc-dc converter ``doubles'' the supply voltage to all the digital circuitry and particularly regulates the time-to-digital converter (TDC) supply to stabilize its resolution, thus maintaining fixed in-band phase noise (PN) across process, voltage, and temperature (PVT). The ADPLL supports a two-point modulation and forms a Bluetooth low-energy (BLE) transmitter realized in 28-nm CMOS. It maintains in-band PN of -106 dBc/Hz [figure of merit (FoM) of -239.2 dB] and rms jitter of 0.86 ps while dissipating only 1.6 mW at 40-MHz reference. The power consumption reduces to 0.8 mW during the BLE transmission when the DCO switches to open loop.

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This paper proposes an ultra-low-voltage (ULV) fractional-N all-digital PLL (ADPLL) powered from a single 0.5 V supply. While its DCO runs directly at 0.5 V, a switched-capacitor DC-DC converter doubles the supply voltage to all the digital circuitry and regulates the TDC supply to stabilize its resolution thus maintaining fixed inband phase noise (PN) across PVT. The ADPLL supports a 2-point modulation and forms a Bluetooth LE (BLE) transmitter realized in 28 nm CMOS. It achieves in-band PN of -106 dBc/Hz (FoM of -239.2 dB) and RMS jitter of 0.86ps while dissipating only 1.6mW at 40 MHz reference. The power consumption reduces to 0.8 mW during BLE transmission when the DCO switches to open-loop.
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