MM74C922WM

The MM74C922WM from On Semiconductor is a CMOS key encoder that provides comprehensive logic for encoding SPST switch arrays. It supports keyboard scanning via an external clock or capacitor and includes on-chip pull-up devices, allowing for switches with up to 50 kΩ on resistance without the need for diodes to prevent ghost switches. The device 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 to a low state when the key is released, even if another key is pressed. This ensures two-key roll-over functionality. An internal register stores the last key pressed. 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 and an operating temperature range of -40°C to 85°C. The encoder is designed for surface mount in a 20-SOIC package. Its low power consumption makes it suitable for various applications requiring efficient key encoding.