Mixed-signal thermometer filtering for low-complexity PLLs/DLLs

A new filtering method significantly reduces DLL/PLL area, power and integration complexity. A compact delay-line structure generates a thermometer-coded control string, in which most bits are held at 0 or 1, but a few cells at the code´s transition point settle into stable analog voltages. Compared to analog circuits, it allows lock-state storage, reduces analog mismatch and leakage, removes control swing limitations on the range, and reduces gain, noise and stability limitations. It removes the quantization jitter of digital versions, but can still be made from standard cells using automated layout