one,
from Vdd.
That's the problem, it should, just like the MSP430 datasheets do.
Because it says under "I/O Ports" that they have Schmitt trigger inputs.
I was hoping Jan would understand that :-)
Microchip is a little more cautious there, with 0.2 and 0.8. But that does not guarantee that it won't switch at 0.3 or even 0.4.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
[snip]
I searched for "hysteresis". Nowhere is that mentioned. I'll ask.
But I'm pretty sure what I'll find is it's simply to clean up slow inputs. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Usually that's the reason, reduces the "oh s..t, it don't work" support requests. But if you need it for noise immunity purposes the hysteresis would have to be known. That's where I must say that TI is a lot more diligent in their specs. Any old thunderstorm would blow a 50mV hysteresis aside but not a 500mV one. Right now about half my assignments are redesigns. Not always fun but it's got to be done.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Cute! Where do you get those 500mV lightning? ;-)
-- Thanks, Fred.
[snip]
I'd expect about a VT (or around 0.35V) for this sort of animal.
A lot of my work is fixing the errors/blunders of others.
Somewhat shocking, I sent a blanket E-mail to about a dozen names I knew from my Microchip oscillator days. Four of them came back "unknown" :-( ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
It's the SMT version, from 0805-size clouds :-)
What I meant is inside a circuit. A properly terminated trace always picks up some, but not a whole lot. So when you have signals that aren't terribly fast you can easily get a double pulse and it knocks some routine off the rocker.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
On a sunny day (Tue, 26 Jan 2010 12:17:19 -0800) it happened Joerg wrote in :
one,
from Vdd.
OK, I see your point, you also want a minimum for input low going up, and a maximum for input high going down.
But the minimum for input low going up is .8 *Vdd, and the maximum for input high going down is .2 * Vdd :-) Nothing else is guaranteed here. Note that that does not exclude the Schmitt trigger effect. thateffect only means it wil flip over and not come back until the otehr border value is reached. Say you start at zero with a positive ramp, it is guaranteed to flip over before you reach 4 V (for 5 V supply), if you then ramp down, it is guaranteed to flip back before you reach 1 V. The real flip over points could be 2 and 3 V... But those have nothing to do with your noise margin, UNLESS you have noise on the input while it is transitioning to cover both limits. I would say in such a case you need a better driving circuit..
That would be great.
Same here but it's not errors per se. Mostly just people looking for a
2nd opinion and then optimizing this, that and the other thing. Very good engineers but it's always best to have folks outside the team reviewing stuff. If all companies would do that we'd have a lot less in schedule slips and re-design rounds.Sometimes it's younger engineers. For example many have never designed a switch mode converter in their life and the prospect of having to do a fairly big one right now drives up their neck hair (it should).
After only two years? Ouch, that is not so good.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
one,
from Vdd.
border value is reached.
That's what it doesn't mean, they do not state anything that says it will not flip until 0.x*VDD.
Aha, now you've got it :-)
With a good micro controller you do not. As I showed the MSP430 specs the hysteresis properly so you can rely on it. You can probably also rely on it with the dsPIC but they failed to spec it. All one (mostly) needs in such cases is the minimum hysteresis. The maximum doesn't matter if you guarantee to get under 0.2*VDD and above 0.8*VDD.
Easy to say "oh just throw in an extra Schmitt up front". But in consumer goods every penny gets turned around and around.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Actually it was 8 years (2002). Time flies when you're having fun ;-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
If you merely told them your name, surely they would recognize your potential sales? ;-)
I think Joel was alluding more to the fact that, regardless of sales numbers, the average user needs to be spoon-fed... imagine Microsoft help lines! They're basically paid to RTFM aloud.
Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
Ha, hire me, it's my hobby ;-)
Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
Doesn't work like that nowadays. You must open a support ticket and enter all that stuff. There are, however, still those "good old day" companies with nearly unconditional support. Linear Technology, Supertex, for example. And from my desk they have been richly rewarded for that with design-ins and subsequent sales. Old American saying: If you don't support your customer, someone else will.
But it doesn't take a rocket scientist on their part to see that a claim is made in a datasheet and the underlying data is clearly missing ;-)
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Seriously, if I needed a hardcore switcher designer I'd probably call you, after having seen some of your stuff on the web. Not many people out there who would grab half a pound of ferrite and run it full bore.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Easy to do...
Slight modification from last month's chip design.
(That enough hysteresis for you, Joerg ?:-) ...Jim Thompson
-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
Sweet. I'd love that but I am afraid the dsPIC ain't gonna be that large in hysteresis. Since I am not a chip designer I can't go in there and fix it :-)
But hey, this year I get to do a high voltage chip. Haven't done one in over ten years. Well, only architecture and guidance, not the transistor level stuff (except for some).
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
On a sunny day (Tue, 26 Jan 2010 15:35:03 -0800) it happened Joerg wrote in :
border value is reached.
No no, I dunno how much you know about micros, but a few points I want to mention here:
1) When an input changes, its is sampled by the micro at some edge of its *own* clock.That means if you have a lousy signal, say a lot of RF noise on a rising edge, like this:
. . . . . . .. . ------------- slice level . .. .
- ---- || | || | ------- micro internal Schmitt output || |
- --
------- | | micro clock ______
^ | data is sampled here, and a '1' is read.
So the input is sampled either low or high, if it sampled low because its sampled just in the low part of the RF, then it will sample high on the next micro clock, just a one clock delay.
I think, the reason, possibly the ONLY reason, for the Schmitt trigger in that input, is to avoid 'metastability'. Now metastability is a whole an other subject, and whole threads have been written on it in comp.arch.fpga, look it up. But it basically is related to the gates operating in their linear range, and the Schmitt trigger really prevents that,
Now on the subject of noise, I have learned that interfacing microns in an industrial environment requires
*always* special precautions. I use opto couplers myself always, simply because that 1) gets rid of ground loops. 2) allows for a wide range of input voltages, say you get something from a 24 V system, or 48 V, or even 230 V. 3) you can likely use the micros internal pullups at the input. 4) Very high frequency RF does not make it through an optocoupler. 5) no capacitive coupling to speak of either. etc etc. So, be smart, and use those.[...]
mention here:
*own* clock.Not if it's an interrupt :-)
like this:
I want this :-)
---- | | |
-------
sampled just in the low part of the RF,
input, is to avoid 'metastability'.
written on it in comp.arch.fpga, look it up.
the Schmitt trigger really prevents that,
Mostly the problem is sluggish inputs or stray noise from nearby thunderstorms. A lightning-induced spectrum concentrates in the hundreds of kHz range and that can produce a lot of grief in a uC. Some of the stuff I deal with is also deployed in the "Tornado Alley", Carribean etc. If you know engineers from the Dutch Antilles they can probably tell you about that.
industrial environment requires
V system, or 48 V, or even 230 V.
It ain't so easy in price-sensitive gear (consumer and so on) where every penny counts. If you can make it happen with a buck less than the other guy your client wins :-)
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
mention here:
*own* clock.edge, like this:
sampled just in the low part of the RF,
that input, is to avoid 'metastability'.
written on it in comp.arch.fpga, look it up.
the Schmitt trigger really prevents that,
industrial environment requires
V system, or 48 V, or even 230 V.
So far, no response from the E-mail I sent to Microchip :-(
Looking at some old Atmel stuff that was purely digital, it should be about 300mV with a 3.3V supply.
Can't you test it ?:-)
BTW: The hysteresis can have it's center located anywhere between
0.2*VDD and 0.8*VDD. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Not too surprising. Thanks for sending the email.
Foundries are a lot more responsive. For one of them I sent the NDA yesterday afternoon and during the night they tossed me the keys to the process data. Plus they are processing some sort of design kit order, whatever than means. Another one immediately scheduled a conference call for early this afternoon. Now that's customer service.
Yes but the hardware is currently 1500 miles from here. However, that won't help too much because I need to know the guaranteed minimum hysteresis.
That would be no problem.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
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