8-bit identity comparator in 20-SOIC
The SN74F521DW is an 8-bit identity comparator from the 74F logic family, packaged in a 20-SOIC (0.295", 7.50mm width) surface-mount package. It compares two 8-bit words and asserts the output when all bits match. The output is active low (A=B), meaning the output goes low when the two 8-bit inputs are identical. This is the standard polarity for cascading multiple comparators in a wider word-width system.
Speed and drive for bus matching
The 74F family's faster switching compared to the 74LS or 74HC series means the SN74F521DW can keep up with higher-speed processor buses without adding wait states. Output drive capability is 1 mA source (high) and 20 mA sink (low). The asymmetric drive is typical for TTL-compatible outputs; the 20 mA sink handles standard TTL fan-out of 10 loads, while the 1 mA source is sufficient for driving CMOS inputs or pull-up resistors. This covers standard 5 V logic rails in indoor equipment — benchtop instruments, telecom line cards, and industrial control boards that stay within a conditioned environment.
Active production and compliance
The tube packaging is the factory-default for SOIC-20; reels are available through distribution on request.