Digital circuit inputs turn on thesholds, turn on voltage?

[Audioguru]

I think I must repeat everything again:
TTL needs a regulated 5V supply. 4.75V to 5.25V ONLY! Look at the datasheet for an old SN7400 IC.
TTL is very old. It uses a lot of supply current. It is fairly fast.
LS TTL uses a little less supply current and is faster.

Ordinary Cmos works from a supply that is 3V to 18V. It uses extremely low supply current but it is fairly slow.
High Speed Cmos works from a supply that is 2V to 7V. It uses very low supply current. It is very fast.

All microprocessors are High Speed Cmos. Most digital memory ICs are Cmos.
Forget about antique TTL.

 

[BradtheRad]

TTL works with 5 volts or 12 volts

Is there anything that TTL can do or can't that CMOS can't do or can do?

For just about every TTL device, you can find a corresponding CMOS device that does the same thing.

Several times when I had need of a particular function for a project, there was a CMOS device that could do it, but no TTL device. Or the CMOS device could do it in one IC whereas TTL would need more than one IC.

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Furthermore I never needed the speed of TTL.

And I like the idea of using IC's that could run on plain voltage from a 9V battery. Whereas TTL would have required a 5V regulator.
Etc.

 

[danny davis]

you can use a 9 volt battery with a TTL , u just using a voltage divider right after the 9 volt battery or 9 volt regulators output

TTL doesn't have ESD problems right? CMOS you have to wear a wrist strap when touching them but with TTL chips you don't have an ESD problem right?

So they make CMOS chips that do the same thing or family of chips that TTL chips do?

 

[Audioguru]

you can use a 9 volt battery with a TTL , u just using a voltage divider right after the 9 volt battery or 9 volt regulators output

Absolutely not!
A voltage divider is not a voltage regulator. When the current increases then the voltage drops. When the current reduces then the voltage increases.
A voltage divider will double the current wasted by the old TTL ICs and the voltage will be wrong anyway.
A little 9V battery cannnot supply the high current used by TTL ICs for much time.
When a little 9V battery quickly runs down to less than 7V then an ordinary 5V regulator will not work.

TTL doesn't have ESD problems right? CMOS you have to wear a wrist strap when touching them but with TTL chips you don't have an ESD problem right?

I am in Canada where there is static electricity EVERYWHERE in winter. I have worked with many Cmos circuits for many years and I have NEVER worn a grounded wrist strap. No Cmos circuit was harmed by static electricity. Cmos has protection circuits and I know how to discharge static electricity on me before I touch Cmos.

So they make CMOS chips that do the same thing or family of chips that TTL chips do?

Of course. Cmos is newer and is better.
Forget about antique TTL.

 

[danny davis]

oh ok so TTL chips Draw a lot of current you're saying

Why does TTL chips draw so much current where CMOS doesn't need to draw much current?

 

[Audioguru]

Why do TTL chips draw so much current where CMOS doesn't need to draw much current?

If you compare their schematics on their datasheets then you will see that TTL uses bipolar transistors. Cmos uses Mosfets. They are completely different.

 

[amirahmadian]

Is there anything that TTL can do or can't that CMOS can't do or can do?

It think Audioguru answered your question:

TTL was fast, not slow. Its high amount of current made it charge and discharge stray capacitance fast.
High Speed Cmos is just as fast, uses very low current and works with a supply from 2V to 7V.

Many digital ICs are available in both TTL family and CMOS family. The main advantage of CMOS is that it uses low power (low current) although it may be slower. This is the main difference but in general you can't say CMOS can do sth that TTL can't or vice versa.

 

[danny davis]

When troubleshooting TTL or CMOS chips, what are some things to look for besides checking the VCC , VEE voltages. Does a tech print out all the data sheets for each logic chip in the circuit and then how does he check the inputs and outputs without removing the chip out of the circuit

 

[Audioguru]

A tech has technical education and experience. He knows what gates and counters do and knows what the logic levels are supposed to be without looking at the datasheets.

 

[danny davis]

A tech has technical education and experience. He knows what gates and counters do and knows what the logic levels are supposed to be without looking at the datasheets.

This is my problem, how do u get to this point of knowing that? without using datasheets

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any rules of thumbs or cheatsheet i can follow

 

[Audioguru]

This is my problem, how do u get to this point of knowing that? without using datasheets

You LEARN it.

any rules of thumbs or cheatsheet i can follow

It is taught in high school, college and university now. When I was in university, TTL and Cmos logic was not invented yet so I learned it from books.
In my electronics carreer I designed very complicated LS TTL and Cmos circuits that worked perfectly the first time they were powered.
I did not fix defective circuits designed by others much because they were extremely reliable.

 

[danny davis]

If you or a tech were given theses IC chips to test in a circuit and troubleshoot, how would u do it?

U8 = CD4046 BCN
U9 = MM 74HC4040N
U10 = NM27C256
U7 = LM339
U6 = MM74HC14N
U11= TL084BCN
U12= TL084BCN
U35= ULN2003
U38 = DCP010505P
U37 = 4N35 opto-coupler
U36 = DS3695N
U33 = MAX202CPE
U28 = CD4051BCN
U41 = DS1305
U31 = MAX522CPA
U27 = TL7757CLP
U29 = MC68HC11E9BCFN2
U15 = ispLSI 1016E-80LJ
U18 = CD4047BE
U24 = 74ACT11240

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U8 = CD4046 BCN
1.) CMOS Phase Locked loop

U9 = MM 74HC4040N
1.) 12 stage Binary Counter

U10 = NM27C256
1.) CMOS EPROm

U7 = LM339
U6 = MM74HC14N
1.) Hex Inverting Schmitt Trigger

U11= TL084BCN
1.) JFET input operational amplifier

U12= TL084BCN

U35= ULN2003
1.) Seven Darlington Arrays

U38 = DCP010505P
1.) Unregulated DC/DC converters
2.) 5 volt input

U37 = 4N35 opto-coupler
U36 = DS3695N
1.) RS485/RS422 Transceivers/Repeaters

U33 = MAX202CPE
1.) 5 volt, RS-232 Transceiver

U28 = CD4051BCN
1.) Dual 4 channel Analog Mulitplexer/ Demultiplexer
2.) 8 channel analog

U41 = DS1305
1.) Serial Alarm real time clock

U31 = MAX522CPA
1.) 8 bit voltage output serial DAC

U27 = TL7757CLP
1.) Voltage Detector

U29 = MC68HC11E9BCFN2
1.) Motorola Microcontroller

U15 = ispLSI 1016E-80LJ
1.) Lattice Semiconductor- in system programmable PLD

U18 = CD4047BE
1.) Monstable/Astable Multivibrator

U24 = 74ACT11240
1.) Octal Buffer/Line Driver with 3 state outputs

U22 = 74HC27
1.) Triple 3 Input NOR gate

 

[FvM]

Rising confusion.

Many of the listed ICs aren't digital logic devices. To test the others, you won't primarly think about logic thresholds. You'll apply full logic level to the inputs and can expect about full level at the output. Unless you are looking for very specific device failure cases or design errors, interpreting logic output as high or low would be sufficient.

 

[danny davis]

How would a tech or you guys test these IC chips, how can I troubleshoot these logic IC chips?

U18 = CD4047BE
1.) Monstable/Astable Multivibrator

U24 = 74ACT11240
1.) Octal Buffer/Line Driver with 3 state outputs

U22 = 74HC27
1.) Triple 3 Input NOR gate

U28 = CD4051BCN
1.) Dual 4 channel Analog Mulitplexer/ Demultiplexer
2.) 8 channel analog

U8 = CD4046 BCN
1.) CMOS Phase Locked loop

U9 = MM 74HC4040N
1.) 12 stage Binary Counter

 

[danny davis]

Why would a troubleshooting tech need to know about each Logic IC chips, Logic Threshold Voltage Levels?

What kind of troubleshooting would a test technician be doing to have to know the logic threshold voltage levels?

When are they used for what use?


Here is a Chart of them:
http://www.interfacebus.com/voltage_threshold.html

 

[FvM]

Why would a troubleshooting tech need to know about each Logic IC chips, Logic Threshold Voltage Levels?

See post #33. I don't think he would. A designer must know however.

 

[danny davis]

How would a tech troubleshoot unexpected state transitions, or the failure to perform state transitions as expected? because of the input logic threshold voltage level?

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But is the Logic IC chips are causing unexpected state transitions, or the failure to perform state transitions as expected? because of the input logic threshold voltage level?

What can a troubleshooting tech do to check or test?

How do a troubleshooting tech narrow down or track down to the component that the Logic IC chips have input logic threshold voltage level has problems?

The Logic IC chips can have the same part number but they have different input logic threshold voltages, this causes unexpected state transitions or failure to perform a state transitions

But how does a troubleshooting tech find which IC chip is doing this or has this kind of problem?

 

[godfreyl]

How would a tech troubleshoot......
What can a troubleshooting tech do......
How do a troubleshooting tech......
But how does a troubleshooting tech......

See post #33.

 

[danny davis]

You'll apply full logic level to the inputs and can expect about full level at the output.

Apply full logic level to the inputs using what? a variable power supply set at +5 volts? I would need multiple power supply's if the IC chip have multiple inputs to check the output of the IC chip right?

 

[godfreyl]

Apply full logic level to the inputs using what?

The chip you're testing is already connected to ground and +5V (or whatever it's supply voltage is). That's all you need. For logic level low, connect the input to ground. For logic level high, connect the input to +5V (or whatever the supply voltage is).