Investigating the effects of transient faults in Programmable Capacitor Arrays

In this work, the effects of transient faults in Programmable Capacitor Arrays (PCA) are investigated. Usually, PCA architectures are built from a set of binary-weighted capacitor branches, which can be connected in parallel. The connection of each branch to the terminals of the capacitor array is programmed through analog switches (usually transmission gates). Transient faults, potentially caused by radiation interaction with the silicon, or by the impact of strongly ionizing particles in sensitive nodes, may temporarily close a switch in the PCA, whose default state should be open. In this case, it may occur a charge sharing process, from the equivalent capacitor (programmed into the PCA) to the temporarily connected capacitor (due to the transient effect). Therefore, after the transient, the voltage stored in the equivalent capacitor may be reduced. This effect is investigated with spice simulations. The influence of the values of the capacitors and the sizing of the analog switches (and its control logic) in the magnitude of the charge sharing effect is also investigated. Finally, some possible design-level mitigation techniques are discussed.