This work presents a low power low- and high-voltage IC design of an asynchronous conditioning circuit assisting the capacitive vibration energy harvester. The proposed IC implements a sensing and control electronics featuring an autocalibration concept, which allows the harvester to adapt to the environmental fluctuations. For the first time such a system is designed to operate at high voltage (up to 30 V). The estimated average power consumption of the IC is less then 1.1uW, whereas the average harvested power is approximately 1.4uW for 14V operation voltage. Current paper is particularly focusing on an ultra-low power (7.3-52)nW clock generator with a programmable frequency (41-265)Hz. The IC design has been carried out in AMS 0.35um high-voltage CMOS technology and has been validated by a coupled VHDL-AMS/SPICE simulation.