A pulse stretcher is disclosed comprising, a stretcher input (10) and a stretcher output (20); an asynchronous finite state machine; and a delay generator (40) having a delay input connected to the stretcher output, and a delay output connected to a second input of the FSM. The asynchronous FSM comprises: a first Muller C-element gate (250) having an output connected to the stretcher output, a second Muller C-element gate (260) having an output; and a combinatorial logic circuit (270) connected to the stretcher input, to first and second inputs of each of the first and second C-elements. The first and second Muller C-element gates are cross-coupled via the combinatorial logic, such that the respective outputs of the C-element gates are complementary and, in response to receiving the input pulse at the stretcher input, the output of the first Muller C-element gate provides a stretched version of the input pulse.