74c14 substitute follow up

Mar 29, 2006 7 Replies

sorry for reposting. I just added some information about voltage rating of two ICs.



---- according to snipped-for-privacy@sunpoint.net :



Yes, you can. It's the number 7414 which tells the purpose of the chip.



The C-letter means it is cmos-type (and it needs to be in your circuit,



as you mentioned), and H means it is high-speed-type. It is not mentioned to be necessary in your circuit, but it is ok to use the high-speed type, although not necessary.


ps. according to the datasheet, 74HC14N is Hex Inverting Schmitt
> Trigger and 74C14 is Hex Schmitt Trigger.

Both ones are inverting. There are mistake, or maybe the maker of the datasheet of the 74C14 has considered the "invertingness" a "special feature" which wouldn't be necessary to tell on the header.


Reply Rate this post:


From: Gerard Bok - view profile Date: Tues, Mar 28 2006 5:16 am Email: snipped-for-privacy@zonnet.nl (Gerard Bok) Groups: sci.electronics.repair Not yet ratedRating: show options


Reply | Reply to Author | Forward | Print | Individual Message | Show original | Report Abuse | Find messages by this author


Yes, you can. It's the number 7414 which tells the purpose of the chip.
>The C-letter means it is cmos-type (and it needs to be in your circuit,
>as you mentioned), and H means it is high-speed-type. It is not
>mentioned to be necessary in your circuit, but it is ok to use the
>high-speed type, although not necessary.

While you are right with the 'general picture' that it is the function that counts, you may well be wrong here :-)


Use in a C-meter, as the poster mentioned, is likely to be dependant on the Schmitt trigger's threshold. And that is one of specs that varies between different technologies :-)


-- Kind regards, Gerard Bok


thanks to replies. According to the datasheet the VCC of of C is higher



than HC part. In the capacitance meter i am planning to make, its supply voltage is 12 volts but 74hc14n VCC pin max is 6 volts only. That might be the problem. With the transistor tester using also 74c14,



its supply voltage is 6 volts. In this case, the 74hc14n might be suited as substitute but not in the capacitance meter with the supply voltage of 12 volts. (Because 74c14 has a Vcc ranging from 3.5-15 v but


74hc14n only up to 6 volts). Am I right?

tnx again,


ian



Okhay, if that is said on the datasheet and ur circuit is using 12V, you're right, that it is a problem, too, although you can correct it by using a 7805 regulator to drop down the Vcc to 5V. But, the problem that Gerard Bok mentioned refers to _threshold_ voltage. It may cause problems if it is different, depending on the circuit. See datasheets if the threshold voltages are mentioned there. But even if not, you can try it if you want. But if u do, remember to use the regulation for Vcc!

good day, let me ask more question please.

I have here 7805 regulator ready for use. I just dont understand if a

12 volt circuit design can be operated on 5 volts. Let me enlighten with this thing. Can it be compatible? Is there no operating differences or malfunction of the circuit because the circuit will operate with lower voltage supply and that might affect the operation because it doesn't go with the circuit design? If it is still works, i'll be glad coz i will not bother to find 74c14 which is not available in my place.

tnx again,

ian

I would stick with the original design and get the C parts. The higher operating voltage may be needed for a particular function of the device.

Jim

I'm very sorry, I was quite careless. Like someones already mentioned, it won't work (and actually the chip will burn) if the signal levels are too high, even though u used proper dropping at the Vcc. You may never use higher signal level than specificated...

Well, actually you can interface 12V CMOS to 5V TTL if you use current limiting resistors between the two familys. For example you can have a

12V high/low feeding into a TTL input if you put a 1.2K resistor in series so the input protection diodes will not be blown, you can output TTL to 12V by using open collector buffers - these (7416s for example) can handle up to 15V with proper design.

Back in the early days MOS (17V) circuits would be directly interfaced to TTL by some clever power supply design - split the 17 supply to

+5/-12 with the TTL running on the +5 section, then use resistors to interface the two families. Look for Gottlieb System 1 MPU schematics for some ideas.

Don Lancaster's CMOS Cookbook covers this TTL/CMOS as well, and I think the TTL Cookbook mentions interfacing as well.

John :-#)#

(Please post followups or tech enquires to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required