The ISL4270E features a VL pin that adjusts the logic pin output levels and input thresholds to values compatible with the VCC powering the external logic (e.g., a UART). This device includes an enhanced automatic powerdown function which powers down the on-chip power-supply and driver circuits. This occurs when all receiver and transmitter inputs detect no signal transitions for a period of 30 seconds. It power back up, automatically, whenever it senses a transition on any transmitter or receiver input. Table 1 summarizes the features of the ISL4270E, while Application Note AN9863 summarizes the features of each device comprising the 3V RS-232 family.