Differential input topologies with immunity to electromagnetic interference

Differential input structures and their immunity to electromagnetic interference (EMI) are discussed and measured. EMI signals coupling into analog circuits can have levels of up to 40 V_pp according to recent industrial EMI specifications [6]. In order to maintain circuit operation under such high disturbances several on chip modifications of standard circuitry are proposed. Low EMI levels can be partly handled by high impedance input structures, whereas for the full EMI specification of 40 V_pp a low input impedance structure has been developed, that prevents ESD clipping by EMI attenuation to the chip voltage range while calibrating for mismatch induced signal deterioration.