Energy Efficient Bio-Feedback Stimulation System with Adaptive Parameters Optimization Closed Loop

Energy efficient bio-feedback stimulation system is implemented for implantable medical device applications. The adaptive parameters optimization (APO) closed loop is proposed to find the most energy efficient values of stimulation parameters including an amplitude (AMP), a pulse-width (PW), a frequency (FREQ) of stimulation currents and a supply of the driver (VDDH). The key mechanism is based on neuron's biologic characteristics; a rheobase current (IRh), a chronaxie time (TCh) and a refractory period (TRefractory). To realize the APO loop, a digital parameters optimizer, an impedance estimator and a programmable current driver is proposed in 180nm HV BCD technology. It forms the closed-loop together with an external neural spike detector and a variable VDDH generator. As a result, the energy consumption can be reduced to less than 1% with the APO closed loop.