8-bit identity match at 4.5 ns
The 74FCT521CTPYG is an 8-bit identity comparator from the 74FCT series, built to compare two 8-bit words and pull the output low when they match. The 4.5 ns max propagation delay at 5 V, 50 pF load means it resolves a match within one fast clock cycle — useful in address decoding, cache tag comparison, or any bus where the match decision must settle before the next rising edge. The active-low output (A=B) is the signal that goes low on a match. In a typical memory-mapped I/O decode, this output enables the chip-select line directly without an extra inverter. The 15 mA source / 48 mA sink drive capability on the output is enough to drive a few CMOS loads or a single TTL input without a buffer.
Supply, temperature, and package fit
The 10 µA quiescent current means it adds negligible static draw to the board, which matters in a multi-card chassis where every milliamp counts toward the PSU budget.