Patent ID: 7405591

Claim:
An apparatus for interfacing a first circuit using a first supply voltage and a second circuit using a second supply voltage different from the first supply voltage, the apparatus comprising: a driver circuit having a driver network comprising driver supply voltage terminals connected to controllable switches, the controllable switches comprising resistive elements or being separated from resistive elements; a receiver circuit having a receiving network comprising a resistive element and receiver supply voltage terminals; and a connection line connecting the driver circuit and the receiving circuit, wherein the controllable switches have two switch configurations, a first switch configuration resulting in a high voltage on the connection line and a second switch configuration resulting in a low voltage on the connection line, wherein the resistive elements in the driver network and the receiver network have values so that a sum of the high voltage and the low voltage is equal to the second supply voltage within a range of 10% of the second supply voltage when the first supply voltage is applied to the driver supply voltage terminals, and when the second supply voltage is applied to the receiver supply voltage terminals.