Interactions between ESD protection devices and other components of a chip can lead to complex and not easily anticipated discharge bevahior. Triggering of a protection MOSFET is equivalent to the closing of a fast switch and can cause substantial transient discharge currents. The peak value of this current depends on the chip capacitance, resistance, properties of the protection clamp, etc. Careful optimization of the protection circuit is therefore necessary to avoid current overstress and circuit failure.