An ESD protection circuit is adapted for an integrated circuit with a first power source and a second power source. The ESD protection circuit comprises a first silicon controlled rectifier (SCR), and in some embodiments a second silicon controlled rectifier, and a parasitic diode. The silicon rectifiers as well as the parasitic diode can all be formed using a single well formed in a substrate. Further, the ESD protection circuit can be used in systems that have multiple power sources regardless of the difference in voltage between the power sources.