[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: 3.3V supply



> If anyone knows why the 9.1% tolerance was specified in the 2.2 spec,
> please let me know.  I find it hard to believe that the spec
> developers
> didn't do their homework at the time and discover 5% tolerance devices
> would be common.
 
"At the time" would be circa 1990.

The JEDEC standard for 3.3V integrated circuits (JESD8-A, 1994)
specifies a VDD range of 3.0 to 3.6V, with no mention of anything
narrower.

Perhaps the question should be, why did IC manufacturers later start to
deviate from existing standards (not just PCI but JEDEC) and specify a
narrower range?

The newer JESD8-B now includes 3.15 to 3.45V as its "Narrow Range," with
3.0 - 3.6V as the "Normal Range" and 2.7 - 3.6V as "Extended Range."

Just how "common" are devices with a 5% supply voltage tolerance?  I
cracked open a T.I. data book of 3.3V parts and they take +/-0.3V just
fine.  I checked some others and they, too, specify 3.0 - 3.6V, if not
wider.  At what point did the exception become the rule?

Regards,
Andy