An ESD clamp includes a first power supply node; an ESD detection circuit coupled to the first power supply node and configured to detect an ESD event; and a bias circuit coupled to the first power supply node and configured to output a second power supply voltage to a second power supply node. The second power supply voltage is lower than a first power supply voltage on the first power supply node. The ESD detection circuit is configured to activate the bias circuit to change working state in response to the ESD event. The ESD clamp further includes an LV ESD clamp coupled to the second power supply node, wherein the LV ESD clamp includes LV devices with maximum endurable voltages lower than the first power supply voltage.