Article View: sci.electronics
Article #18384Re: TTL (and other) families
From: William Swan
Date: Tue, 19 Jan 1988 17:36
Date: Tue, 19 Jan 1988 17:36
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1511 bytes
In article <143@Giraf.dde.uucp> mbe@dde.uucp (Martin Berg) writes:
>> Also note that 74HCT parts will consume *much* more current when driven...
>There is another problem when using this family of TTL.:
>
>Last when I read TI's specifikations on the 74HCT family, it was made
>clear that this family needed at least 4.5 V supply voltage.
>
>Therefore you should not use these parts (for reliable operation)
>in applications with a low-voltage, low-power standby mode (f.ex.
>for preserving contents of CMOS-RAM).
>[...]
>My question is: Has the specifications changed or are these parts
>better than promised ?
The specifications are as you mentioned. I took a look at some other
manufacturer's specs, and they are the same. It appears that HCT is
fairly limited (probably as a result of whatever is done to shift the
threshold on these devices).
For an example, the specifications given by Universal Semiconductor
are as follows:
VCC: Min Max
74HCxx 2.0V 6.0V
74HCTxx 4.5V 5.5V
--
William Swan {ihnp4,decvax,allegra,...}!uw-beaver!tikal!sigma!bill
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!uw-beaver!tikal!sigma!bill From: bill@sigma.UUCP (William Swan) Newsgroups: sci.electronics Subject: Re: TTL (and other) families Message-ID: <1460@sigma.UUCP> Date: 19 Jan 88 17:36:33 GMT References: <2040@navajo.UUCP> <1457@sigma.UUCP> <143@Giraf.dde.uucp> Reply-To: bill@sigma.UUCP (William Swan) Organization: Summation Inc, Kirkland WA Lines: 28