A 0.5GHz 0.35mW LDO-Powered Constant-Slope Phase Interpolator with 0.22% INL

Clock generators are an essential and critical building block of any communication link, whether it be wired or wireless, and they are increasingly critical given the push for lower I/O power and higher bandwidth in Systems-on-Chip (SoCs) for the Internet-of-Things (IoT). One recurrent issue with clock generators is multiple-phase generation, especially for low-power applications; several methods of phase generation have been proposed, one of which is phase interpolation. We propose a phase interpolator (PI) that employs the concept of constant-slope operation. Consequently, a low-power highly-linear operation is coupled with the wide dynamic range (i.e., phase wrapping) capabilities of a PI. Furthermore, the PI is powered by a low-dropout regulator (LDO) supporting fast transient operation. Implemented in 65-nm CMOS technology, it consumes 350μ W at a 1.2-V supply and a 0.5-GHz clock; it achieves energy efficiency 4× -15× lower than state-of-the-art (SoA) digital-to-time converters (DTCs) and an integral non-linearity (INL) of 2.5× -3.1× better than SoA PIs, striking a good balance between linearity and energy efficiency.