A timing control circuit comprises at least three current control units coupled in parallel between a first circuit and a second circuit node. The current control units each have an active mode and an inactive mode. The current control units are responsive to a timing trigger event to pass current whose magnitude is dependent on how many of the current control units are in the active mode. The current control units comprise a plurality of groups. Current control units within a same group are responsive to a change in a bit of a control value corresponding to that group to switch together between the active and inactive modes, such that the magnitude of the current is dependent on which of the groups are in the active mode. The signal timing in the associated circuit is varied in dependence on the magnitude of the current.