General Description

These synchronous presettable counters feature an internal carry look ahead for cascading in high speed counting applications. The DM74AS169 is a 4-bit binary up/down counter. The carry output is decoded to prevent spikes during normal mode of counting operation. Synchronous operation is provided 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 clock input waveform.

These counters are fully programmable; that is, the outputs may each be preset either HIGH or LOW. The load input circuitry allows loading with carry-enable output of cascaded counters. As loading is synchronous, setting up a LOW level at the load input disables the counter and causes the outputs to agree with the data inputs after the next clock pulse.

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