74HC191S

The 74HC191 is a 4-bit synchronous presettable up/down binary counter designed using CMOS process technology, consisting of four D flip-flops and additional gate circuits. A low-active synchronous preset input, Load, enables presetting of the output state. A count mode control input, D/U̅, selects either up-counting or down-counting operation. An output count enable control input, CTEN, is used to stop or hold the count. When CTEN is driven low, the output state is clocked on the rising edge of the clock to perform counting; when CTEN is driven high, counting stops and the outputs are held at their current state, but R̅C̅O̅ goes high. Two carry outputs, R̅C̅O̅ and MAX/MIN, produce a pulse upon overflow at the end of a counting cycle. In down-counting mode, the pulse is generated when the count reaches zero; in up-counting mode, the pulse is generated when the count reaches its maximum value. R̅C̅O̅, when this condition is met, outputs a low pulse only while CLK is low, with a duration approximately equal to the low-level pulse width of CLK. MAX/MIN outputs a high pulse with a duration approximately equal to one complete period of CLK. These two outputs can be used to cascade multiple counters for expanded counting capacity.

Applications

• Digital/counter logic drive
• Industrial control

Key features

• Low input current: ≤ 1uA @ VCC = 6V
• Wide operating voltage range: 2.0V ~ 6.0V
• Clock rising edge triggered
• Supports multi-chip cascade expansion
• 4-bit synchronous presettable up/down binary counter
• 2 carry output pulses
• Output capable of driving up to 10 LSTTL loads
• Package types: DIP16, SOP16