Maker Pro
Maker Pro

MM74HC164 - Freq limits at 3.3V?

Hi,
Im using MM74HC164 in my project as a serial to parallel converter and
my question is if i give 3.3V as Vcc (supply voltage) what may be its
operating frequency, can please some one help me out in finding this...
 
M

martin griffith

Jan 1, 1970
0
On 11 Feb 2007 22:22:00 -0800, in sci.electronics.design
Hi,
Im using MM74HC164 in my project as a serial to parallel converter and
my question is if i give 3.3V as Vcc (supply voltage) what may be its
operating frequency, can please some one help me out in finding this...

It is in the datasheet, page 4 in the fairchild version, or maybe you
didn't ask the right question


martin
 
W

Winfield Hill

Jan 1, 1970
0
Im using MM74HC164 in my project as a serial to parallel converter and
my question is if i give 3.3V as Vcc (supply voltage) what may be its
operating frequency, can please some one help me out in finding this...

There are logic families meant for faster operation at low supply
voltages, than the old 74HC parts, . For example the 74vhc family
is specified down to 2.0 volts. The 74vhc164 can shift to 125MHz
typical (or to 80MHz minimum), at 3.3V and 25C, according to the
datasheet, http://www.fairchildsemi.com/pf/74/74VHC164.html
 
F

Fred Bloggs

Jan 1, 1970
0
Im using MM74HC164 in my project as a serial to parallel converter and
my question is if i give 3.3V as Vcc (supply voltage) what may be its
operating frequency, can please some one help me out in finding this...

Every datasheet known to mankind will list the maximum frequency versus
Vcc in the "timing" section. First and foremost before undertaking a
digital design is to learn how to read datasheets. How come you don't
know how to do this?
 
W

Winfield Hill

Jan 1, 1970
0
Every datasheet known to mankind will list the maximum frequency versus
Vcc in the "timing" section. First and foremost before undertaking a
digital design is to learn how to read datasheets. How come you don't
know how to do this?

Well, Fairchild's 74hc164 datasheet doesn't say anything about
operation at 3.3 volts. It says the worst-case minimum is 5 MHz
at 2V, and 27 MHz at 4.5 volts, 25C. Such a huge spec variation
from 5 to 27MHz makes it hard to estimate the operation at 3.3V
and is one good reason to simply avoid using the hc logic family
at low voltages. This is especially so when there are plenty of
much better choices, like the 80MHz at 3.3V 74vhc164 I suggested.
 
W

Winfield Hill

Jan 1, 1970
0
Well, Fairchild's 74hc164 datasheet doesn't say anything about
operation at 3.3 volts. It says the worst-case minimum is 5 MHz
at 2V, and 27 MHz at 4.5 volts, 25C. Such a huge spec variation
from 5 to 27MHz makes it hard to estimate the operation at 3.3V
and is one good reason to simply avoid using the hc logic family
at low voltages. This is especially so when there are plenty of
much better choices, like the 80MHz at 3.3V 74vhc164 I suggested.

OK, maybe it's not quite that simple. I see most distributors don't
carry the 74vhc164. DigiKey and Newark don't, although Mouser does.
The 74ac164 could be an alternate choice, DigiKey and Mouser have
it, although Newark doesn't. The 74ac164 is spec'd at 62MHz min at
3.3V for the -40C TO +85C temp range. Hell, it'll even do 7Mhz at
1.5 volts. Now that's getting doowwn!

BTW, when it comes to finding the logic families you want in stock,
it gets rather difficult if you insist on a particular IC package.
For example, I like the thin ssop SMD package, TSSOP, which is both
space-saving and reasonable to hand solder. But many MSI parts are
not offered in that package, or if they are, they're not stocked.
 
J

Joerg

Jan 1, 1970
0
Winfield Hill wrote:


[...]
BTW, when it comes to finding the logic families you want in stock,
it gets rather difficult if you insist on a particular IC package.
For example, I like the thin ssop SMD package, TSSOP, which is both
space-saving and reasonable to hand solder. ...


Man, you must have good eyes. In my designs I need to use TSSOP a lot
but really hate it when I have to swap one of these out.
 
W

Winfield Hill

Jan 1, 1970
0
Joerg said:
Winfield Hill wrote:

[...]
BTW, when it comes to finding the logic families you want in stock,
it gets rather difficult if you insist on a particular IC package.
For example, I like the thin ssop SMD package, TSSOP, which is both
space-saving and reasonable to hand solder. ...

Man, you must have good eyes. In my designs I need to use TSSOP
a lot but really hate it when I have to swap one of these out.

It's not so bad if you're using a Metcal soldering station
and have a Talon handle (which has two tips), with the right
tip, TATC-502. The whole IC comes off at once in a hurry.
 
R

Riscy

Jan 1, 1970
0
It is in the datasheet, page 4 in the fairchild version, or maybe you
didn't ask the right question

martin

This family should work both 5V and 3V3 system
 
J

Joerg

Jan 1, 1970
0
Winfield said:
Yes it works, but not well.

I've used HC logic under 3V, a lot. Ok, it becomes a bit sluggish but
sometimes there isn't much of a choice when you want widely available
parts. For example, right now I need an 8-bit equality comparator and
other stuff for bus slot and address detection. There ain't much else in
stock than HC688 and the like. The other guys want to run the bus at
3.3V. It's spec'd at 2V and 4.5V but not at 3.3V so I must probably use
the 2V spec unless I find one that has 3.3V in the data sheet.

Guess I'll have to post a speed limit on the bus, hoping the other guys
won't pelt me for that ;-)
 
Top