74AC11160

This synchronous, presettable 4-bit decade counter features an internal carry look-ahead circuitry for application in high-speed counting designs. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the count-enable inputs and internal gating. This mode of operation eliminates the output counting spikes that are normally associated with asynchronous (ripple clock) counters; however, counting spikes may occur on the ripple carry out output (RCO). A buffered clock input triggers the four flip-flops on the rising (positive-going) edge of the clock input waveform.

This counter is fully programmable in that they may be preset to any number between 0 and 9. As presetting is synchronous, setting up a low level at the load input disables the counter and causes the outputs to agree with the setup data after the next clock pulse, regardless of the levels of the enable inputs. The clear function for the 74AC11160 is synchronous and a low level at the clear input sets all four of the flip-flops outputs low, regardless of the levels of the clock, load, or enable inputs.

If one of these decade counters of the 74AC11160 is preset to a number between 10 and 15 or assumes such an invalid state when power is applied, it will progress to the normal sequence within two counts as shown in the state diagram.

The carry look-ahead circuitry provides for cascading counters of the 74AC11160 for n-bit synchronous applications without additional gating. Instrumental in accomplishing this function are two count-enable inputs and a ripple carry output. Both count-enable inputs (ENP and ENT) must be high to count, and ENT is fed forward to enable the ripple carry output (RCO). RCO thus enabled will produce a high-level pulse while the count is 9 (HLLH). This high-level overflow ripple carry pulse can be used to enable successive cascaded stages. Transitions at the ENP or ENT are allowed regardless of the level of the clock input.

This counter features of the 74AC11160 a fully independent clock circuit. Changes at control inputs (ENP, ENT, orLOAD) that will modify the operating mode have no effect on the contents of the counter until clocking occurs. The function of the counter (whether enabled, disabled, loading, or counting) will be dictated solely by the conditions meeting the setup and hold times.

The 74AC11160 is characterized for operation from 40°C to 85°C.