Ultra low power ring VCO based tuneable signal generator for neural stimulation

In this paper an integrated circuit capable of generating low frequency signals is presented. These low frequency signals are useful in Deep Brain Stimulation of neural cell which is a therapy of Parkinson´s disease. Using sub-threshold circuit design concepts and techniques, the proposed circuit can produce low frequency signals from a current starved voltage controlled ring oscillator. Using a supply voltage of 0.4 V the designed circuit can generate frequencies between 97.5 Hz to 428.5 Hz by tuning the control voltage between 0 V to 0.4 V. It consumes a maximum power of 11.1nW and gives a maximum frequency deviation of ±4.2% for a noisy supply voltage of voltage deviation of maximum ±5mV (ΔVDD). It shows good rail to rail operation with perfect square wave of 52% duty cycle, which is useful in DBS for Parkinson´s disease treatment (frequency required for PD is 130 Hz to 185 Hz).