An 8GHz, 0.005mm2 all digital clock generator having 0.1% frequency accuracy by new ZTC algorithm

This work proposes an all digital clock generator (ADCG) with a new PVT compensation technique to generate a stable and accurate frequency over wide frequency ranges up to 8GHz. To compensate frequency variations by temperature changes, a novel Zero Temperature Coefficient (ZTC) algorithm using mutual compensation between the mobility and the threshold voltage of devices has been implemented. The proposed scheme achieves frequency accuracy of 0.1% or less over wide temperature ranges without any external reference clock. The experimental results of an ADCG having automatic ZTC algorithm in 28nm CMOS technology show 104 dB FOM, low power (0.49mW per GHz) and tiny size (0.005mm
²
).