Path: 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

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