Level-shifter circuit for integrated circuits

Abstract

A level-shifter circuit includes a deep N-tank to insulate the N-channel portions of transistors from the substrate. The circuit is formed on a P-type substrate coupled to reference voltage Vss. A first field-effect transistor has first and second N+ doped regions formed in a third isolating P- doped region. The third doped region is formed in a fourth isolating N- doped region, which is formed in the substrate. A second transistor has first and second N+ doped regions formed in the same isolation regions as those of the first transistor. A third field-effect transistor has first and second P+ doped regions formed in an isolating N- region that is formed in the substrate. A fourth field-effect transistor has first and second N+ doped regions formed in the same isolation N- region as that of the third transistor. The gate of the first transistor is coupled to a first input. The first doped region of the first transistor is coupled to the output and the second doped region of the first transistor is coupled to the negative voltage Vn. The third doped region is coupled to the negative voltage Vn and the fourth doped region is coupled to the supply voltage Vdd. The second transistor is connected in feedback configuration to the first transistor. The gate of the third transistor is coupled to the second input. The first doped region of the third transistor is coupled to the output and the second doped region of the third transistor is coupled to the voltage Vp, which is more positive than the supply voltage Vdd. The fifth doped region of the third transistor is also coupled to the voltage Vp. The fourth transistor is connected in feedback configuration to the third transistor.