A programmable muscle stimulator based on dual-slope charge balance

This paper presents a single-channel programmable muscle stimulator. The charge balance of the proposed stimulator is achieved using the concept of the dual-slope analog-to-digital converter (ADC). This approach negates the need for precise current matching between cathodic and anodic current, which is usually required in order to achieve good charge balance. In the dual-slope concept, the charge on the integrating capacitor is proportional to the charges delivered during the cathodic phase. When charges on the integrating capacitor are fully discharged during anodic phase, charge balance is achieved. The proposed stimulator is demonstrated in a 0.35μm CMOS technology. Measurement results show that the stimulator is indeed able to produce balanced biphasic stimuli of different amplitudes and pulse-widths. Charge imbalance is in the range of nano-coulombs, well within the safety tolerance for muscle stimulation.