SN74LS390N(XBLW)

The SN74LS390 is a dual 4-bit decade ripple counter divided into four independent clocked sections. The counter contains 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 BCD decade or binary-coded quinary configurations. If the master reset inputs 1MR and 2MR are used to simultaneously clear all 8 bits of the counter, multiple counting configurations can be realized within a single package. The section clocks nCP0 and nCP1 support ripple counter or frequency division applications, enabling divide ratios of 2, 4, 5, 10, 20, 25, 50, or 100. The high-to-low transition of 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 binary-coded 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 clock and forces all four outputs LOW. Inputs include clamping diodes to support interfacing inputs to voltages exceeding VCC using current-limiting resistors.

Key features

• Dual BCD decade or binary divide-by-five counters
• Single device configurable as divide-by-2, 4, 5, 10, 20, 25, 50, or 100 divider
• Two master reset inputs for independent clearing of each decade counter
• Operating temperature range: -20°C ~ +85°C
• Package options: DIP-16, SOP-16, TSSOP-16