Apparatus and methods enable robust, reliable control for implantable medical devices, including cardiac pacemakers, defibrillators and cardiac resynchronization devices. Integrated circuits in the devices have minimized interfaces, can derive power from the interface signals, and have high voltage and latch-up protection. A device lead has a power generation circuit and a switching circuit using cascaded PMOS transistors for operating with a stable voltage despite fluctuations in the supplied voltage. The lead has control electronics that provide a very low impedance between an electrode and a lead conductor during most of the duration of a pacing pulse, but during a brief initial portion of the pacing pulse, provide a very high impedance to permit charging up a power supply that is local to the control electronics. A method of stabilizing the external impedance and a system for fault detection and fault recovery for an implantable device are also provided.