特性 Features

? Positive or Negative Edge Triggering

? Synchronous Internal Carry Propagation

? Fanout (Over Temperature Range)

- Standard Outputs . . . . . . . . . . . . . . . 10 LSTTL Loads

- Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads

? Wide Operating Temperature Range . . . -55oC to 125oC

? Balanced Propagation Delay and Transition Times

? Significant Power Reduction Compared to LSTTL

Logic ICs

? HC Types

- 2V to 6V Operation

- High Noise Immunity: NIL = 30%, NIH = 30% of VCC

at VCC = 5V

? HCT Types

- 4.5V to 5.5V Operation

- Direct LSTTL Input Logic Compatibility,

VIL= 0.8V (Max), VIH = 2V (Min)

- CMOS Input Compatibility, Il ≤ 1μA at VOL, VOH

描述 Description

The CD74HC4518 is a dual BCD up-counter. The ’HC4520

and CD74HCT4520 are dual binary up-counters. Each

device consists of two independent internally synchronous

4-stage counters. The counter stages are D-type flip-flops

having interchangeable CLOCK and ENABLE lines for

incrementing on either the positive-going or the negativegoing

transition of CLOCK. The counters are cleared by high

levels on the MASTER RESET lines. The counter can be

cascaded in the ripple mode by connecting Q3 to the

ENABLE input of the subsequent counter while the CLOCK

input of the latter is held low.