Hysteresis on dsPIC ports?
in [Design]
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From: Joerg on 27 Jan 2010 14:09 WangoTango wrote: > In article <7sbcbtFv25U1(a)mid.individual.net>, invalid(a)invalid.invalid > says... >> >>> 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. >> >> 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 :-) > > A buck less AND it has to work. It will. > Is what you are working on going to be produced in such vast numbers > that 25 cents here or there is going to be the difference between making > or breaking the profit margin? > I find that a reliable product is a lot easier to sell than one that is > just 'cheap'. > This one just has to be small. I can make uC products work very reliably without fancy circuitry around them, have done it many times. _If_ the uC is properly characterized, which this one is not. I would not have picked it but was already in there. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joel Koltner on 27 Jan 2010 14:16 "Joerg" <invalid(a)invalid.invalid> wrote in message news:7sbhbmFt77U1(a)mid.individual.net... > This one just has to be small. I can make uC products work very reliably > without fancy circuitry around them, have done it many times. _If_ the uC is > properly characterized, which this one is not. I would not have picked it > but was already in there. What's the cost of fixing the many flaky internal power-on reset circuits that you've seen many of? :-)
From: Joerg on 27 Jan 2010 14:22 Joel Koltner wrote: > "Joerg" <invalid(a)invalid.invalid> wrote in message > news:7sbhbmFt77U1(a)mid.individual.net... >> This one just has to be small. I can make uC products work very >> reliably without fancy circuitry around them, have done it many times. >> _If_ the uC is properly characterized, which this one is not. I would >> not have picked it but was already in there. > > What's the cost of fixing the many flaky internal power-on reset > circuits that you've seen many of? :-) > In terms of components? Well under 50c, even in IC form. These little dudes are quite nice at around 15c a pop in qties: http://www.onsemi.com/pub_link/Collateral/NCP302-D.PDF The cost to the business before the fix? Huge. Because it often results in a service call, or a truck roll in utility speak. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 27 Jan 2010 14:37 On Wed, 27 Jan 2010 10:07:59 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: > >[...] > >> So far, no response from the E-mail I sent to Microchip :-( >> > >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. > > >> 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 ?:-) >> > >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. > > >> BTW: The hysteresis can have it's center located anywhere between >> 0.2*VDD and 0.8*VDD. >> > >That would be no problem. They've probably never measured it, just inserted a library part ;-) You _do_ know that you can safely put an R/C in front of a Schmitt input to get rid of large HF noise? I came up with that VT/VBE from rail hysteresis gimmick (posted earlier today) during my ignition pick-up days... around 40 years ago... rejects even severe spark noise ;-) ...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.
From: Jim Thompson on 27 Jan 2010 14:41
On Wed, 27 Jan 2010 11:22:02 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Joel Koltner wrote: >> "Joerg" <invalid(a)invalid.invalid> wrote in message >> news:7sbhbmFt77U1(a)mid.individual.net... >>> This one just has to be small. I can make uC products work very >>> reliably without fancy circuitry around them, have done it many times. >>> _If_ the uC is properly characterized, which this one is not. I would >>> not have picked it but was already in there. >> >> What's the cost of fixing the many flaky internal power-on reset >> circuits that you've seen many of? :-) >> > >In terms of components? Well under 50c, even in IC form. These little >dudes are quite nice at around 15c a pop in qties: > >http://www.onsemi.com/pub_link/Collateral/NCP302-D.PDF > >The cost to the business before the fix? Huge. Because it often results >in a service call, or a truck roll in utility speak. Done right, it's quite a bit of circuitry. One I did recently, that tested 3 supplies plus had a delay after voltages were AOK, was close to 15% of the active chip area :-( ...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. |