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Grounding the unused terminals of TTL ICs

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A.Anand Srinivasan

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TTL ICs

my friend hat the unused terminals of an TTL IC is to be grounded because most of them are open collector
but he didn't know why we are to do that and what would happen if we don't do that
i find that the ICs are perfect even without this kind of grounding
can someone help me?
 

albert22

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Re: TTL ICs

With TTL ICs I would connect the unused INPUTS to a pullup (a resistor to 5 volts).
One resistor can be used as a pullup to several inputs.
As far as I know there is no need to connect the OC outputs to gnd. Do not connect other outputs to gnd or vcc because it could damage the IC.
 

zolam

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Re: TTL ICs

its forbiden to ground OC outputs directly.
it will absolutely damages the IC
maybe you heard something about connecting them to vcc via a resistor ?
 

Kral

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Re: TTL ICs

A.Anand Srinivasan,

Unused TTL inputs are noise susceptible. Even if a whole section of a TTL module is unused, the inputs should be at a known state. Otherwise the outputs will bang up and down, creating EMI.
 

IanP

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Re: TTL ICs

Unused TTL OC outputs can be, without causing any damage to the IC, connected to 0V (GND) but you will not gain anything, as open-collector outputs either drive their outputs LOW or let them float ..
Don't connect them to Vcc, as this can damage the output transustors, and better leave them unconnected ..

Different story with TTL/CMOS inputs, but that is not what you were concerned about .. and was addressed by Kral ..

Regards,
IanP
 

electronics_kumar

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TTL ICs

THE CASE isdifferent for CMOS IC's what i mean it will not create any state in the input side as like in TTL inwhich unused freely left will be taken as logic high...correct me if i am wrong..
 

Santoshalagawadi

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Re: TTL ICs

see most of the TTL Ic's are manufactured using LSI technology
which contains around 1000 trnsistor during manufacturing and one of the advantage is that it can operate at 12v that is high voltage

The IC such as 7400 7408 7486 are all TTL IC's

if you want more information on TTL you cn refer to the following websit

www.datasheet.com
 

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