A time-to-digital converter (TDC) comprises a first delay line including a plurality of first delay cells connected in series, wherein each of the first delay cells include a plurality of first delay units connected in series, wherein each of the first delay units includes a tunable PMOS transistor, a first poly on oxide definition (OD) edge (PODE) transistor, and a pull-up PMOS transistor. The TDC further comprises a second delay line including a plurality of second delay cells connected in series, wherein each of the second delay cells include a plurality of second delay units connected in series, wherein each of the second delay units includes a tunable NMOS transistor, a second PODE transistor, and a pull-down NMOS transistor.