Dual 4-bit Decade Ripple Counter IC - 74HC390

Dual 4-bit Decade Ripple Counter IC - 74HC390

The 74HC Series 74HC390 IC is a 16 Pin Dual 4-bit Decade Ripple Counter IC having a 2V to 6V Operating Voltage range. It has been divided into four separately clocked sections. The counters have two divide-by-2 sections and two divide-by-5 sections. These sections share an asynchronous master reset input (nMR) and can be used in a BCD decade or bi-quinary configuration. If master reset inputs 1MR and 2MR are used to clear all 8 bits of the counter simultaneously, numerous counting configurations are possible within one package.

Section clocks nCP0 and nCP1, allow ripple counter or frequency division applications of divide-by-2, 4, 5, 10, 20, 25, 50 or 100. The HIGH-to-LOW transition of the clock inputs nCP0 and nCP1 triggers each section. 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 nQ3 output is connected to the nCP0 input and nQ0 becomes the decade output. A HIGH on the nMR input overrides the clocks and sets the four outputs LOW. Inputs include clamp diodes. It enables the use of current-limiting resistors to interface inputs to voltages in excess of VCC.

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