Interface chips: between logic and a hard place

摘要

Logic signals have fallen from the 15V of the old CMOS 4000 series to 5V TTL (transistor-to-transistor rnlogic) to modern CMOS levels of 3.3, 2.7, and 1.8 V. Advanced processes use digital logic that operates at 1V or lower, although they offer higher I/O voltages. These ever-dropping logic voltages still must drive solenoids, twisted-pair wiring, and discrete-semiconductor-power stages, so they require external interface circuits. You need to understand rnthese circuits, which run the gamut from FET drivers to open-collector solenoid drivers to LVDS (low-voltage-differential-signaling) and isolated drivers.