EMRFD Message Archive 5269
Message Date From Subject 5269 2010-09-28 05:08:23 Kenneth Stringham [RE]: 74G74 replacement for 74S74
The 74G74 is not a direct replacement for the 74S74. This 3.6v technology
compared to the S74 which is 5v technology. The maximum supply voltage is
specified as 4.6v compared to 5.75v for the S74.
There is a sufficient amount of clocking speed for this device to divide the
200MHz. The specified maximum clocking speed is 600MHz for the G74.
Concerning driving a 50 ohm load, these devices were designed to drive this type
of load. I've used the 74S140 device in a number of designs where I was driving
50 ohms, so this would work, but the mismatch between technologies might be a
problem.
As far as driving a 50 ohm line of a three (3) inch distance, there is no issue.
Three (3) inches is an extremely short length of line compared to the wavelength
here. I don't know what the load is that will be driving. If it is not 50 ohms,
you could try a twisted pair with a 200 ohm load. The 74G74 should be able to
drive this length of line.
A more modern device for this application would something like a 74AG74.
Ken - AE1X5272 2010-09-28 06:21:38 Tim Re: [RE]: 74G74 replacement for 74S74 5274 2010-09-28 06:44:45 ehydra Re: [RE]: 74G74 replacement for 74S74
But I never seen the AG version.
- Henry
--
ehydra.dyndns.info
Tim schrieb:
> Dumb question from someone who has only slowly kept up with the 74x00 series logic families over the years....
>
> Where I can I find a datasheet for e.g. 74G74 or 74AG74?
>
> My usual suspects (Digikey, Mouser, TI, Fairchild websites) don't turn up anything useful. I suspect I have to prepend something like "SN94AG" to all these part numbers to get to something a search engine will find...
>
> I thought I was doing pretty good by keeping up with the 74AC series (which BTW can make quite good drivers) but that probably came out 15 years ago now and the 74G has me stumped.
>
>5275 2010-09-28 07:03:29 Andy Re: [RE]: 74G74 replacement for 74S74
That worked for me, for the 74G74.
But I don't know what a 74AG74 is (Google doesn't find it either). Is
there such a line of logic parts?
Andy