IC 74154 DATASHEET PDF

Integrated Circuit. Transistor Transistor Logic (TTL). 4−Line−to−16−Line Decoder /Demultiplexer. 24−Lead DIP Type Package. Description: The NTE is a. 1) CPD is defined as the value of the IC’s internal equivalent capacitance which is calculated from the operating current consumption without load. (Refer to Test . datasheet, circuit, data sheet: NSC – 4-Line to Line for Electronic Components and Semiconductors, integrated circuits, diodes, triacs.

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The active-low enable inputs allow cascading of demultiplexers over many bits. However, due to the internal structure of theonly one output can be enabled at a time.

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Datasheet(PDF) – National Semiconductor (TI)

You can upvote more than one answer. I am a new user so I didn’t know I had that power. If you wanted to generate a 1 of demultiplexer, you could use 16 s looking at the 4 least significant bits, while a single would look at the 4 most significant bits, with one ouput going to each of the other 16 s.

Why is the output in the truth table inverted in a ic used as a demux?

Why are the outputs inverted? I understand how it works.

National Semiconductor

It is counterintuitive yes, but it is a well-established convention that the sort of devices that this part will be controlling will have active-low enable inputs. The active-low output is just how the design for that specific decoder was carried out – there is also active-high varieties. High speed signals were usually active low, for much the same reason. The demultiplexing function is performed by using the 4 input lines to address the output line, passing data from one of the strobe inputs with the other strobe input low.

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Sign up or log in Sign up using Google. I have a doubt in the demultiplexer section. This all has to do with the actual ic design. Rather than providing only a single enable, both pins are used.

(PDF) 74154 Datasheet download

Inputs were pulled high by default, and only pulled low when necessary, to save power. This chip is often used in demultiplexing applications, such as digital clocks, LED matrices, and other graphical outputs. Each of the 16 outputs can be connected through a resistor and then through an LED to serve as a simple 16 LED controller.

Home Questions Tags Users Unanswered. According to the internal logic diagram on the datasheet, the G inputs are connected to a two-input AND gate with inverting inputs, whose output feeds one input of all the NAND gates that produce the outputs. But when we try to implement a demultiplexer using a TTLthis is the truth table that is given in the book: If you want to know exactly what is going on then draw out the truth table, but it is unlikely their function will make much sense to you.

Is the hardware implementation circuit different than the one explained in theory? Sign up or log in Sign up using Google. So you can use a 47 kilohm resistor to pull up drops 1. For example, if the target application requires 16 7-segment LED displays, but your microcontroller only has 4 lines to select which display is active, this chip 74LS would provide a very effective method of essentially multiplying you selecting lines by a 4 times. All inputs are buffered and input clamping diodes are provided to minimize transmission-line effects and thereby simplify system design.

Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. Each or these 4-line-toline decoders utilizes TTL circuitry to decode four binary-coded inputs into one of sixteen mutually exclusive outputs when both the strobe inputs, G1 and G2, are low.

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By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. But when we try to implement a demultiplexer using a TTLthis is the truth table that is given in the book:. There are probably two enable inputs because otherwise there would be two unused pins on the 24 pin package I don’t recall seeing 22 pin DIP packages.

Post as a guest Name. Email Required, but never shown. The person who took time to answer the question will appreciate that. This allows more flexibility in the logic functions available.

Will someone please explain the purpose of inverting the outputs 0 through 15 as well as the use the NAND gates here? By clicking “Post Your Answer”, you acknowledge that you have read satasheet updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. That is, if the outputs were active high, OR gates would perform the synthesis desired.

Sign up using Email dagasheet Password. WhatRoughBeast 49k 2 28 The LED can be chosen at random by the status of the 4 line selector inputs.

National Semiconductor – datasheet pdf

Post as a guest Name. The actual implementation of the chosen ic has active low outputs.

Many TTL parts and older memory chips have active low enable inputs, so the active low outputs of this part can be connected directly to those inputs. So theory will cover only the theory which explains the basic functionality of the working of a demultiplexor.

Please consider upvoting those questions you found useful like this one by clicking the arrow pointing up near the answer vote count which is in turn above the checkbox you clicked to accept this question. And this carried through to the way the logic was used, and designed with.

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