DM7490AN

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The DM7490AN (also referred to as the 74ls90) is the most popular member of the chip family that includes the 74ls93, 74ls94 and 74ls96. It is a four-bit binary ripple counter or divider, which means that it can count to fifteen (20H) or divide an incoming signal by fifteen.

The DM7490AN\'s application field is mainly in sequential logic circuits. It can be used in generating periodic voltage waveforms for clock signals and other timing applications. It can also be used for counting, frequency division, and decimal counting.

The working principle of the DM7490AN is based on the concept of ripple counting. Ripple counting involves the use of synchronous (or clock-controlled) logic devices such as flip-flops and the passage of pulse signals (or the “ripples”) through the chain of these devices.

In the case of the DM7490AN, the chain consists of four flip-flops, each of which has two outputs (Q’ and Q”) and one input (D). The input signal is injected into the first flip-flop through the D input and then flows out of the first flip-flop through one of its two outputs. The signal then flows into the next flip-flop through the same output and then out of the second flip-flop through the other output. This process continues such that the signal travels through the chain and eventually reaches the fourth flip-flop.

At the end of the ripple, the flip-flops are set to their respective outputs which correspond to a number in binary. This binary number indicates the number of ripple pulses that were received. The DM7490AN uses this technique to count pulses or divide frequencies.

The DM7490AN also has two additional inputs, the reset (R) and preset (P) inputs. These inputs set the flip-flops to output “0” and “1” respectively and can be used for resetting or setting the number of pulses. This allows the chip to act both as a counter (in which each pulse increases the number of ripples) and a divider (in which each pulse decreases the number of ripples).

In summary, the DM7490AN is a four-bit binary ripple counter and divider that is used in sequential logic circuits. It works on the concept of ripple counting and has two additional inputs for resetting and setting the number of pulses. It can be used for counting, frequency division, and decimal counting.

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