Post by thread:Internal Oscillators

Hi Again I missed that one and looking at the line card it looks like I should have looked a little closer before asking that question. There are 10 devices listed under "Future Products" which will have an on board oscillator. Does anyone have any info on release dates? Later, Charles (Thanks Dave) {Quote hidden}>> >> >> >Date: Tue, 27 Jan 1998 10:30:07 -0800 (PST) >> >From: spam_OUTdaverTakeThisOuTauspex.com (Dave Reinagel) >> >To: .....cjoachimKILLspam@spam@HOTMAIL.COM >> >Subject: Re: Internal Oscillators >> > >> > >> >PIC14000 >> > >> >> From owner-piclistKILLspamMITVMA.MIT.EDU Tue Jan 27 10:22:56 1998 >> >> X-Originating-IP: [199.212.89.104] >> >> Content-Type> : > text/plain> >> >> Reply-To: pic microcontroller discussion list >> <.....PICLISTKILLspam.....MITVMA.MIT.EDU> >> >> Sender: pic microcontroller discussion list <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU> >> >> Subject: Internal Oscillators >> >> To: PICLISTspam_OUTMITVMA.MIT.EDU >> >> Content-Length: 488 >> >> X-Lines: 15 >> >> >> >> Hi All >> >> >> >> I was wondering if anyone here (Microchip People?) know if Microchip >> >> plans to offer internal oscillators on devices other than the >> PIC12CXXX. >> >> Seems like logical thing to do. Probably bring the cost of many >> >> applications down, probably more reliable, simpler circuits..... I'm >> >> just looking for your opinions here... so give em to me... but not >> too >> >> hard. >> >> >> >> Later >> >> >> >> Charles >> >> ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com

Charles, Thanks for bringing this up Charles - I think it's a great topic. From my experience with working directly with Microchip, I'd say that there is an excellent chance they will do this - eventually (measured, unfortunately, in several years of time - but the success of the 12CXXX family already should have convinced them to offer such a version in all the PIC families). I designed a very high volume product around the 12C509 (millions of units/yr., although, it hasn't shipped - yet -), and did EXTENSIVE lab testing on the internal oscillator - it's a pretty rock-solid design. I've even met with Microchip directly, and worked with the manufacturing/test engineers to better characterize and fine tune our oscillator requirements in our particular application. (BTW, don't expect to ever be able to talk to these guys yourself unless you're an incredibly large volume customer - and then only maybe...) I'm not saying that they changed anything for us, but we had a much more guarantee-able design after they "ran the numbers" for us (read: truly characterized the oscillator through extensive wafer testing). I firmly support you in your appeal to Microchip to increase the number of devices that contain an internal RC oscillator. I think everyone benefits. But - and everyone else out there should be aware of some important issues when applying this particular feature of any PIC - ESPECIALLY when it is first introduced to us (and even more importantly when devices are made available in "Engineering" type samples): 1) Any new chip they apply the internal oscillator technology to needs to be FULLY CHARACTERIZED by Microchip before I'd EVER use it. They typically SIMULATE the design and release preliminary data sheets with projected device characteristics... Things (osc. characteristics) will likely change after they build a few wafers and test for process corners... For me, after they had performed serious wafer test, I found that the projected osc. characteristics became WORSE... But, fortunately in my case, I was able to find a way around it. 2) Any of your designs need to seriously take into consideration: a) Temp range, b) Typical Vdd operating point and range (especially supply regulation). c) +/- 3 sigma process variation (at least) of the chip. These parametrics will affect the oscillator frequency more than anything else... 3) If you need to guarantee better than a 2.5%-3% tolerance on Fosc over ALL operating conditions, you're better off using a resonator or xtal, because you're sure to see the corners of their process tolerances in any kind of volume... To more directly address your original points: 1) I saved about 25-30 cents [includes all costs] per widget by using the internal RC osc. This includes all direct, indirect and typical hidden costs (p.c. real estate needed, pick and place costs, component stocking costs, improved reliability, etc.). Keep in mind that my volume is (was) between 20-30 MM units/yr for a several year period. Your savings will likely be even higher (perhaps as much as $1?). 2) My design was far more elegant because of the internal osc. design... 3) And reliable... 4) I also needed all the I/O I could get in an 8 pin device. This is the only way to maximize I/O capabilities of the 12CXXX family... 5) I also believed it may have helped in reducing my total RFI emmision signature for various reasons that I can't go into here... So, from a very real world example (sorry - can't disclose what the widget is or does - due to one of those annoying proprietary/trade secret clauses in an employee exit agreement), I can assure you the internal RC osc. is a great way to go if you do not have strict real-time timing issues. I suspect that a vast majority of personal/hobby/non mission-critical PIC projects could probably get away with using this type of cost-improving oscillator. I just wish the folks at Microchip would consider using a better (more temperature and voltage stable) internal osc. technology. I know for a fact that if they wanted to, they could tighten the tolerances to under 1%, and not necessarily at higher chip cost (I've researched the various fundamental methods, and it's quite doable). SO: HOW ABOUT IT MICROCHIP??? Chuck Mauro > {Original Message removed}

> >From my experience with working directly with Microchip, I'd say that > there is an excellent chance they will do this - eventually (measured, > unfortunately, in several years of time - but the success of the 12CXXX > family already should have convinced them to offer such a version in all > the PIC families). I would also say that Scenix may provide them with some extra incentive to do this, as they have the internal osc feature as well (also an 8 bit divider down to 32kHz which is quite a good idea). > 3) If you need to guarantee better than a 2.5%-3% tolerance on Fosc over > ALL operating conditions, you're better off using a resonator or xtal, The Scenix datasheet mentions 8%. Not that it really matters. Either you need time accuracy (resonator) or you don't (Ext/Int RC). I don't really care if I debounce a button for 30ms or 50ms if I'm using it to turn on a relay or light bulb. As you point out, the real estate saving is significant. An HC49U crystal is bigger than the 12C509 and if you go to a smaller footprint part, the price jumps substantially. They've wet our appetite. Now we want more ! :-) > 5) I also believed it may have helped in reducing my total RFI emmision > signature for various reasons that I can't go into here... It would be interesting to see some data on that. (Not from you obviously. You'd have to shoot me) I'd like to see a comparison between Xtal, external RC and internal osc. Just as a guess, I wouldn't be suprised if the external RC was the worst. Anyone have the right gear ? Steve. ====================================================== Very funny Scotty. Now beam down my clothes. ====================================================== Steve Baldwin Electronic Product Design TLA Microsystems Ltd Microcontroller Specialists PO Box 15-680 email: @spam@stevebKILLspamkcbbs.gen.nz New Lynn, Auckland ph +64 9 820-2221 New Zealand fax +64 9 820-1929 ======================================================

Chuck: Yes, you are right! Low TC internal IC oscillator technology is available - since the early 80's. Since you have close contact within Microchip you should suggest they hire a sharp analog engineer (or get a cross-license) from a top analog IC house - like Analog Devices, Dallas Semiconductor, or Maxim. They have oscillators cells, like their bandgap references and charge transfer A/Ds, that give ppm performance over temperature. They know about die attach, packaging parameter shifts and how to trim with laser and e-squared trimming. Microchip may be too digitally inbred to know the proven production solutions are out there. - Wayne Foletta BMI - Saratoga, CA {Quote hidden}> ---------- > From: Mauro, Chuck[SMTP:KILLspamChuck.MauroKILLspamKLA-TENCOR.COM] > Reply To: pic microcontroller discussion list > Sent: Tuesday, January 27, 1998 12:14 PM > To: RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU > Subject: Re: Internal Oscillators > > Charles, > > Thanks for bringing this up Charles - I think it's a great topic. > > From my experience with working directly with Microchip, I'd say that > there is an excellent chance they will do this - eventually (measured, > unfortunately, in several years of time - but the success of the > 12CXXX > family already should have convinced them to offer such a version in > all > the PIC families). > > I designed a very high volume product around the 12C509 (millions of > units/yr., although, it hasn't shipped - yet -), and did EXTENSIVE lab > testing on the internal oscillator - it's a pretty rock-solid design. > I've even met with Microchip directly, and worked with the > manufacturing/test engineers to better characterize and fine tune our > oscillator requirements in our particular application. (BTW, don't > expect to ever be able to talk to these guys yourself unless you're an > incredibly large volume customer - and then only maybe...) I'm not > saying that they changed anything for us, but we had a much more > guarantee-able design after they "ran the numbers" for us (read: truly > characterized the oscillator through extensive wafer testing). > > I firmly support you in your appeal to Microchip to increase the > number > of devices that contain an internal RC oscillator. I think everyone > benefits. But - and everyone else out there should be aware of some > important issues when applying this particular feature of any PIC - > ESPECIALLY when it is first introduced to us (and even more > importantly > when devices are made available in "Engineering" type samples): > > 1) Any new chip they apply the internal oscillator technology to > needs > to be FULLY CHARACTERIZED by Microchip before I'd EVER use it. They > typically SIMULATE the design and release preliminary data sheets with > projected device characteristics... Things (osc. characteristics) > will > likely change after they build a few wafers and test for process > corners... For me, after they had performed serious wafer test, I > found > that the projected osc. characteristics became WORSE... But, > fortunately in my case, I was able to find a way around it. > > 2) Any of your designs need to seriously take into consideration: > > a) Temp range, > b) Typical Vdd operating point and range (especially supply > regulation). > c) +/- 3 sigma process variation (at least) of the chip. > > These parametrics will affect the oscillator frequency more than > anything else... > > 3) If you need to guarantee better than a 2.5%-3% tolerance on Fosc > over > ALL operating conditions, you're better off using a resonator or xtal, > because you're sure to see the corners of their process tolerances in > any kind of volume... > > > To more directly address your original points: > > 1) I saved about 25-30 cents [includes all costs] per widget by using > the internal RC osc. This includes all direct, indirect and typical > hidden costs (p.c. real estate needed, pick and place costs, component > stocking costs, improved reliability, etc.). Keep in mind that my > volume is (was) between 20-30 MM units/yr for a several year period. > Your savings will likely be even higher (perhaps as much as $1?). > > 2) My design was far more elegant because of the internal osc. > design... > > 3) And reliable... > > 4) I also needed all the I/O I could get in an 8 pin device. This is > the only way to maximize I/O capabilities of the 12CXXX family... > > 5) I also believed it may have helped in reducing my total RFI > emmision > signature for various reasons that I can't go into here... > > So, from a very real world example (sorry - can't disclose what the > widget is or does - due to one of those annoying proprietary/trade > secret clauses in an employee exit agreement), I can assure you the > internal RC osc. is a great way to go if you do not have strict > real-time timing issues. I suspect that a vast majority of > personal/hobby/non mission-critical PIC projects could probably get > away > with using this type of cost-improving oscillator. > > I just wish the folks at Microchip would consider using a better (more > temperature and voltage stable) internal osc. technology. I know for > a > fact that if they wanted to, they could tighten the tolerances to > under > 1%, and not necessarily at higher chip cost (I've researched the > various > fundamental methods, and it's quite doable). > > SO: HOW ABOUT IT MICROCHIP??? > > > Chuck Mauro > > > {Original Message removed}

> I would have thought it would be possible to apply brownout > protection via Vcc rather than MCLR, in other words you can imagine > a brownout protection circuit that in essence consisted of a low > dropout regulator (I believe you can get devices with <100mV > dropout) controlled by a brownout circuit that in the event of a > brownout would pull Vcc to 0V and leave it there until the main > supply returned to normal. This might work. Why in the heck is this not built into regulators in the first place? I have always wondered. {Quote hidden}> > Also, I've been thinking about this brownout issue. In essence we're > trying to preserve the sanity of the processor. Given that most > brownouts are of fairly brief duration, and that normally the PIC > chip isn't driving significant current from its ports (and I prefer > not to drive current from the ports since normally you want things > like ULN2003 drivers etc. between your PIC and the real world - > which if nothing else also protect against transients coming back > the other way), then wouldn't one of those backup capacitors (1F) > work quite well at keeping the PIC Vcc at nominal during the > brownout. THe problem comes when the device is first turned on, there has not bveen enough time to charge up the backup capacitor yet. If a brownout occurs at this time, or is still occurring after the cap has discharged, then the micro can go into LALA land. Maybe this is OK in a toy or a VCR controller. I work with driving heating elements, and those can be very dangerous if the micro gets stuck while one is turned on. A definite brownout circuit that pulls MCLR down always halts the processor, and that's the insurance I need. Best Regards, Lawrence Lile