This document discusses among other things apparatus and methods for protecting circuit elements from harmful voltages. In an example, an apparatus can include an amplifier configured to receive an input signal and to provide an estimate of a first output signal, a peak detector to receive the estimate and to generate a comparison signal that is active when the amplified input signal exceeds a threshold value, and a timer configured to activate a second output signal if the comparison signal is active for at least a selected time period. The timer can include a first digital input and the selected time period can be set using a state of the first digital input.