9.1.6 Noise Immunity

The input sensitivity of a standard RS-485 transceiver is ±200 mV. When the differential input voltage, V_ID, is greater than +200 mV, the receiver output turns high, for V_ID < –200 mV the receiver outputs low.

The SN65HVD888 transceiver implements high receiver noise-immunity by providing a typical positive-going input threshold of 35 mV and a minimum hysteresis of 40 mV. In the case of a noisy input condition therefore, a differential noise voltage of up to 40 mV_PP can be present without causing the receiver output to change states from high to low.