HEF4518BT

The HEF4518B is a dual 4-bit internally synchronous BCD counter from Philips Semiconductors. It offers active HIGH clock inputs (CP0) and active LOW clock inputs (CP1), allowing flexibility in clocking or enabling functions. An active HIGH overriding asynchronous master reset (MR) ensures immediate reset of the counter.

This counter advances on either the LOW to HIGH transition of CP0 when CP1 is HIGH, or the HIGH to LOW transition of CP1 when CP0 is LOW. The Schmitt-trigger action on the clock inputs provides tolerance to slower clock rise and fall times. Typical propagation delay from clock input to output is 93 ns at 50 pF load.

The HEF4518B is available in a 16-lead SO (SOT109-1) package, suitable for surface mounting. Applications include multistage synchronous and asynchronous counting, and frequency division.

Key electrical characteristics include propagation delays and output transition times, with typical values provided for various conditions. The device is designed for reliable operation with tolerance to varying clock signal characteristics.