Methods for responding to an electrostatic discharge (ESD) event on a voltage rail, ESD protection circuits, and design structures for an ESD protection circuit. An RC network of the ESD protection circuit includes a capacitor coupled to a field effect transistor at a node. The node of the RC network is coupled with an input of the inverter. The field-effect transistor is coupled with an output of the inverter. In response to an ESD event, a trigger signal is supplied from the RC network to the input of the inverter, which drives a clamp device to discharge current from the ESD event from the voltage rail. An RC time constant of the RC network is increased in response to the ESD event to sustain the discharge of the current by the clamp device.