高速CMOS逻辑双路同步计数器 High-Speed CMOS Logic Dual Synchronous Counters
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 negative going 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.
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 . . . -55°C to 125°C
• 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 VCCat 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
