A negative voltage level shifter circuit includes a pair of input transistors, a gate of each input transistor being driven by one of an input signal and an inverted version of the input signal, a cascode sub-circuit coupled to the pair of input transistors, and a pair of cross-coupled transistors for locking a state of the voltage level shifter depending on the input signal, wherein respective gates of the cross-coupled transistors are driven by outputs of respective comparator sub-circuits.