Jim Thompson wrote:
Spehro Pefhany wrote:
On Tue, 25 Jun 2013 22:21:52 -0700, Michael Karas
[This followup was posted to sci.electronics.design and a copy was sent
to the cited author.]
DC will never exceed 5V and abs max is 5.8V. So you think ESD or
surges
(the usual machine-gun style bursts in EMC tests) are ok? We have it
clamped to a 5V rail but it could really lean into those clamp diodes.
This thread rattles around avoiding specifics. Is the "5V-tolerant"
input an input that has 3.3V as VDD?
Yes, the SiLabs C8051F020 type part nominally uses a 3.3V supply for the
I/O Rail VDD. These pins default to typical 8051 style with quasi-
bidirectional behavior with onboard pullup circuitry. The port pins can
also be programmed to be output driven by a totem pole output to the VDD
rail.
I'd (thankfully) almost forgotten about those miserable quasi
bi-directional port pins.
The schematic on page 161 does not appear to show the brief hard
(~100:1) pullup on 0->1 port-pin transition that old-skule 80C51s
have. If it's present it would be back of the ESD circuitry anyway.
https://www.silabs.com/Support Documents/TechnicalDocs/C8051F02x.pdf
The problem is that, as usual, they write nothing about what's in the
Schmitt buffer at the bottom of that schematic. Sometimes I wish IC
designers were closer to the board level world and thus release more of
the info that we really need. Because we board level guys have to deal
with ESD pulses, RF bursts, nearby lightning, and whatnot. And then like
in this case we have to get the whole thing through myriad agency certs
which require good rationale and math.
It's management. Note how LTspice is going all encrypted?
You meant damagement?
And Analog Devices modeling efforts are now managed by a MARKETING VP,
and they are ultimately heading to requiring simulation of their parts
ONLY on their web-based simulator.
That would be a marketing decision that borders on stupid.
I was there (San Jose) last August trying to convince them of the best
way to do modeling... let me see the real netlist and then I'd match
it behaviorally. The MARKETING VP nixed the idea.
(I even showed them various posts from this newsgroup complaining
about model quality... did no good.)