Sounds like standard CMOS inputs, no schmitts. There is no explicit suggestion of SCR latchup or high shoot-thru currents overheating the chip; the poorly-worded cautions seem to be about noise, although overheating is another hazard. The warnings are pretty much standard CMOS practice.
The data sheet doesn't mention allowable input pin current, which sometimes suggests a latchup hazard.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
Schmitt, or not, CMOS inputs should not be floated (unless they have built-in pull-ups or pull-downs) because they are high impedance and can wander anywhere due to board leakage. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions.
hey can have excessive current in the input stage due to cross conduction
ices)
Instead of current, they list the voltage:
Qoute (page 41)
Do not input signals or an I/O pull-up power supply to ports other than 5-V tolerant ports while the device is not powered. The current injection that results from input of such a signal or I/O pull- up may cause malfunction and the abnormal current that passes in the device at this time may cause degradation of internal element s. Even if ?0.3 to +6.5 V is input to 5-V tolerant ports, it will not cause problems such as damage to the MCU.
Unqoute
So, 0.3V over whatever diode they have in the input
Sure, but it should not cause a malfunction. Some discrete schmitt triggers has a defined max cross conduction current, so in some cases it should be possible to leave it open, although it is not good engineering practice
The question is, how much current can you force into an ESD diode of a powered chip, before it latches up and fries? Some parts specify that; be cautious if they don't.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
o they can have excessive current in the input stage due to cross conductio n
devices)
5-V tolerant ports while the device is not powered.
ll-up may cause malfunction and the abnormal current that
ents.
ot cause problems such as damage to the MCU.
It's just another way to put it. 0.3V across the diode translates to a curr ent. I would rarther have the current specified, but the voltage is ok also , granted that the latchup state current really is temperature correlated
, so they can have excessive current in the input stage due to cross conduc tion
er devices)
he
d
an 5-V tolerant ports while the device is not powered.
pull-up may cause malfunction and the abnormal current that
lements.
l not cause problems such as damage to the MCU.
The LM139? (LM339 in dip?) That's always given me 'fits' with power on. I think I had to beef up the positive rail. (?) or RC delayed one rail?? A better behaved comparator would be nice.
ut, so they can have excessive current in the input stage due to cross cond uction
ther devices)
it
the
ard
than 5-V tolerant ports while the device is not powered.
/O pull-up may cause malfunction and the abnormal current that
elements.
ill not cause problems such as damage to the MCU.
a
t;
BITD National used LM1xx/2xx/3xx to refer to the same chip in military, ind ustrial/automotive, and commercial temperature grades, respectively.
So the LM139 was the cerdip/metal can version of the 339, with the 239 in t he middle. So we have the LM111/211/311 comparator, LM109/209/309 regulato r, and so on.
A nice Schottky rectifier from each supply to ground fixes a lot of those s orts of ills.
For a somewhat faster cheap OC comparator, I use a certain number of LM319s and 311s, but I generally don't use a lot of comparators these days.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.