An Integrated Charge Pump for Phase-Locked Loop Applications in Harsh Environments

Among all the functions that electronics currently perform, clock synthesis has a backbone role. Charge pump phase-locked loops (CP-PLL) are widely used to accomplish clock synthesis thanks to their versatility. One of the most critical parts of CP-PLLs is the charge pump, which greatly influences the system's performance. Even though several high-performance charge pumps have been proposed in the past, with the quick spread of electronics in all the engineering fields, the design of such electronic devices has encountered several additional challenges dictated by external environmental conditions. Examples of these engineering sectors are space, aerospace, industrial, and automotive applications, where the charge pump has to face high environmental temperatures and radiation effects. As a consequence, its design and experimental characterization have to be performed to ensure reliability when operating in harsh conditions. However, to the best of the authors' knowledge, no works in the literature have ever presented a complete charge pump design and characterization in such harsh environments. Therefore, to fill this gap, this paper presents a charge pump for PLL applications specifically designed to reach operating temperatures up to 200 degrees C and total ionizing dose levels up to 100 Mrad. All design choices have been experimentally verified and are discussed throughout the paper in detail. With the proposed design, we obtained an output current variation of less than 8% at 200 degrees C and less than 2.5% at 100 Mrad. As opposed to the CPs that can be found in the literature, these results were measured on silicon. The performed measurements confirm that the current variation at 200 degrees C is better than that of the state-of-the-art CPs operating at lower temperatures, which, moreover, were only simulated.