XNOR gate — equality checker for harsh environments
The Texas Instruments CD74HC7266E is a quad 2-input XNOR (Exclusive NOR) gate from the 74HC high-speed CMOS logic family. An XNOR output goes HIGH when both inputs match — it is the fundamental building block for digital equality detection, controlled inversion, and parity-check logic. With four independent gates in a single 14-DIP package, this part consolidates board-level compare functions into one DIP footprint. Rated across the full military temperature range of -55°C to 125°C, this is not a commercial or industrial-grade gate. It is specified for designs that must function reliably in avionics, satellite, missile guidance, or downhole instrumentation where the ambient temperature swings well beyond the -40°C to 85°C industrial band. The 14-DIP through-hole package is a natural fit for prototyping, socketed breadboards, and legacy-system repair — not for high-volume SMT assembly.
Supply range and logic compatibility
The 2V to 6V supply range means the CD74HC7266E can be powered from a 3.3V or 5V rail directly, without a level translator at the supply pin. The input logic levels scale with VCC: at 5V, a LOW is typically below 1.8V and a HIGH above 1.5V, which is compatible with standard 5V CMOS and TTL families. For a 3.3V system, the thresholds shift proportionally — still cleanly driven by a 3.3V microcontroller output. Each output sources or sinks 5.2mA — enough to drive a single LS TTL load or a low-power LED indicator, but not a relay coil or high-fanout bus. For heavier loads, buffer the output with a discrete transistor or a dedicated line driver.
30 ns propagation delay — timing budget context
The 30ns maximum propagation delay at 6V and 50pF load (typical is lower) places this gate in the moderate-speed tier. It is fast enough for control logic, status decoding, and clock-enable generation at a few MHz, but not for high-speed data paths running above 10 MHz. When cascading several gates in a critical timing path, sum the delays against your clock period — 30ns per stage adds up quickly.
Lifecycle and sourcing reality
The CD74HC7266E carries an Active lifecycle status and is ROHS3 compliant. The 14-DIP through-hole package ships in Tube form.