Re: 3V3 in, 5V out buffer driver

Jim Thompson wrote...
Winfield Hill wrote:
Jim Thompson wrote...

Agent dumps old threads after 10 days so I can't go back and look, but
I believe it was on the order of 4-5mA, which I consider unacceptable
for static consumption. Maybe the OP will return with his data ??

I doubt it was that high. If so, we need to know what manufacturer,
because it's far above the clearly-stated maximum specs.

My main point is: WHY do it when good-engineering-practice solutions
exist? Of course, if you're a hacker, who cares ;-)

Why cast aspersions against standard industry practice,

Really ?:-)

especially when your suggested LVC alternate simply can't work?
What are you suggesting instead?

I note that ON Semi's mc74vhc1gt32 (were you involved with that
product?) specifically states "to be used as a logic?level
translator from 3.0 V CMOS logic to 5.0 V CMOS Logic", yet it has
exactly the same "problem" and draws 1.5mA max for 3.4-volt inputs
with 5V supply, just like the standard hct and vhct logic families.

I showed a schematic awhile back that had no such current. The *true*
logic translators usually have two VDD's... one at 3.3V and one at 5V.

Yes, I'm very familiar with at least some of those designs, having
used them for 5V to 12V logic-translation in the days when every
microamp counted, and a few times I had to roll my own with discrete
parts. I didn't see your schematic, but the ones I worked with had
inverters running off the LV rail to present two out-of-phase signals
to two n-mos transistors wired in a flip-flop running off the HV rail,
followed by HV inverters to buffer the output. One had to be careful
the HV rail didn't go below the LV rail during supply sequencing.

We need a part number for such a circuit for the 2.0 to 3.3V world.

I don't recognize "VHC"... the stuff I did was "LCX"; and there's a
project file that I know of only as "TinyCkts"... I don't know what
naming convention those ended up under.

VHC is one of today's very popular muti-sourced low-voltage cmos
families. ON Semi makes 'em as well.

Are there any LCX parts that are specified to operate with 5V-supply
rails? I see only up to 3.3V specified. Some allow rails even up
to 7V, but give no guidance as to proper operation above 3.3 volts.
ON Semi's 74LCX14 has an input-threshold vs. supply plot that shows
one can't expect proper low-V logic tolerances for Vcc above 3.6V.
So LCX is out, unless there's a special part.

Google doesn't give any hits for TinyCkts. Are you referring to
ON Semi's MiniGate families like the NL17, NL27 and NL37, etc.?
Do they include any 5V-supply parts? I haven't found any.


--
Thanks,
- Win
.

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