General Description

These synchronous presettable counters feature an internal carry look ahead for application in high speed counting designs. The DM74ALS162B is a four-bit decade counter, while the DM74ALS161B and DM74ALS163B are four-bit binary counters. The DM74ALS161B clears asynchronously, while the DM74ALS162B and DM74ALS163B clear synchronously. The carry output is decoded to prevent spikes during normal counting mode of operation. Synchronous operation is provided by having all flip-flops clocked simultaneously so that outputs change coincident with each other when so instructed by count enable inputs and internal gating. This mode of operation eliminates the output counting spikes which are normally associated with asynchronous (ripple clock) counters. A buffered clock input triggers the four flip-flops on the rising (positive going) edge of the clock input waveform.

特性 Features

■ Switching specifications at 50 pF

■ Switching specifications guaranteed over full temperature and VCC range

■ Advanced oxide-isolated, ion-implanted Schottky TTL process

■ Functionally and pin-for-pin compatible with Schottky and low power Schottky TTL counterpart

■ Improved AC performance over Schottky and low power Schottky counterparts

■ Synchronously programmable

■ Internal look ahead for fast counting

■ Carry output for n-bit cascading

■ Synchronous counting

■ Load control line

■ ESD inputs