MM74C923N

The MM74C923N from On Semiconductor is a CMOS key encoder IC that provides complete logic for encoding an array of SPST switches. It supports keyboard scanning via an external clock or capacitor and includes on-chip pull-up devices for switches up to 50 kΩ on resistance, eliminating the need for diodes to prevent ghost switches.

This encoder features an internal debounce circuit that requires a single external capacitor and can be disabled by omitting the capacitor. A 'Data Available' output signals a valid keyboard entry, returning low when the key is released. It supports two-key roll-over and has a last key register at its outputs. The 3-STATE outputs are LPTTL compatible, facilitating easy expansion and bus operation.

Key specifications include a wide supply voltage range of 3V to 15V, an operating temperature range of -40°C to 85°C, and a 20-DIP package suitable for through-hole mounting. The device offers low power consumption and is designed for efficient keyboard matrix encoding.

Applications for the MM74C923N include custom keyboard designs, data entry terminals, and any system requiring reliable matrix switch encoding. Its robust design and features like keybounce elimination and two-key roll-over ensure accurate data input.