Patent ID: 8305721
Filing Date: 2012-11-06
Classification: H02H

Abstract:
1. An electrostatic discharge protection device for protecting an inner circuit, the inner circuit operated in a source voltage and receiving an input voltage through a pad, the electrostatic discharge protection device comprising: a protection unit providing a discharge path transmitting an electrostatic signal from the pad to a ground line, the protection unit having a control end and adjusting a holding voltage and a triggering voltage for determining whether to conduct the discharge path based on a voltage level at the control end; and a control unit transmitting the input voltage to the control end of the protection unit when the source voltage is supplied, such that the protection unit raises the holding voltage and the triggering voltage, the control unit switching the control end of the protection unit to a floating condition or a ground condition by the electrostatic signal when the source voltage is not supplied, such that the protection unit lowers the holding voltage and the triggering voltage, wherein the control unit comprises: a first capacitor, a first end of the first capacitor being electrically connected to the pad; a first n-type transistor, a drain of the first n-type transistor being electrically connected to a second end of the first capacitor, a source of the first n-type transistor being electrically connected to the ground line, a gate of the first n-type transistor receiving the source voltage; a first inverter disposed between the pad and the ground line, an input end of the first inverter being electrically connected to the second end of the first capacitor; and a first isolating circuit, a first end of the first isolating circuit being electrically connected to an output end of the first inverter, a second end of the first isolating circuit being electrically connected to the control end of the protection unit, the first end and the second end of the first isolating circuit being conducted when a voltage level at the first end of the first isolating circuit is greater than a voltage level at the second end of the first isolating circuit.