CD74HCT390

高速 CMOS 逻辑双路十进制纹波计数器

The CD74HC390 and ’HCT390 dual 4-bit decade ripple counters are high-speed silicon-gate CMOS devices and are pin compatible with low-power Schottky TTL LSTTL. These devices are divided into four separately clocked sections. The counters have two divide-by-2 sections and two divide-by-5 sections. These sections are normally used in a BCD decade or bi quinary configuration, since they share a common master reset nMR. If the two master reset inputs 1MR and 2MR are used to simultaneously clear all 8 bits of the counter, a number of counting configurations are possible within one package. The separate clock inputs nCP0\ and nCP1\\ of each section allow ripple counter or frequency division applications of divide-by-2, 4. 5, 10, 20, 25, 50 or 100. Each section is triggered by the High-to-Low transition of the input pulses nCP0\ and nCP1\\.

For BCD decade operation, the nQ0 output is connected to the nCP1\ input of the divide-by-5 section. For bi-quinary decade operation, the nO3 output is connected to the nCP0\ input and nQ0 becomes the decade output.

The master reset inputs 1MR and 2MR are active-High asynchronous inputs to each decade counter which operates on the portion of the counter identified by the "1" and "2" prefixes in the pin configuration. A High level on the nMR input overrides the clock and sets the four outputs Low.

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Two BCD Decade or Bi-Quinary Counters

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One Package Can Be Configured to Divide-by-2, 4, 5,10, 20, 25, 50 or 100

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Two Master Reset Inputs to Clear Each Decade Counter Individually

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Fanout Over Temperature Range

\- Standard Outputs...10 LSTTL Loads

\- Bus Driver Outputs...15 LSTTL Loads

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Wide Operating Temperature Range... -55°C to 125°C

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Balanced Propagation Delay and Transition Times

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Significant Power Reduction Compared to LSTTL Logic ICs

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HC Types

\- 2V to 6V Operation

\- High Noise Immunity: NIL = 30%, NIH = 30% of VCC at VCC = 5V

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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

Data sheet acquired from Harris Semiconductor