The use of closed-loop implantable telemetry devices is increasing as recent clinical studies have shown their efficiency and usefulness in detecting and treating various cardiac arrhythmias. In this paper, we present a single-chip closed-loop system providing closed-loop feedback of sensed cardiac patterns. This device promises more optimized stimulation parameters to cure rapid arrhythmias compared with open-loop devices. Our system incorporates more functionality comparing with the conventional micro-stimulators, yet consumes less power. It is powered by implanted rechargeable batteries periodically charged by radio-frequency (RF) coupling. This improvement of the powering system can prevent improper device operation or shutdown due to RF coupling and loading variations. Furthermore, this system eliminates the need for periodic surgery for battery replacement and improves quality of life of the patient. In this work, an implantable micro-stimulator SoC (IMSoC) is designed as cardiac defibrillator for remote delivery of power by means of coupled coils supplying power to a bio-implanted rechargeable battery. The IMSoC consists of a smart control circuit for power management, an RF-coupling power system for battery charging and 2 ultra-small rechargeable batteries as power supplies. The micro-stimulator circuit embedded in the IMSoC is externally powered and controlled by a single encoded RF carrier. Stimulus parameters, such as pulse width, amplitude, and frequency, can be programmed from the remote controller.