Post by thread:32khz osc problems

Today I had an 32khz XTAL startup problem, that was obviously caused by a too small load capacitance. For the product it is essential that the PIC always runs. Therefore I want to make further reliability tests with the XTAL and caps. What is the worst case condition for voltage and temperature, under which a marginally connected XTAL is most likely to fail? I have set the PIC to LP mode, if that matters.

We use LP mode at 32KHz a lot. Have you considered the reliability of this under varying humidity. You need to carefully consider how you protect your PCB. We use 12pF both sides and keep all leads short. James Wilson spam_OUTjwilsonTakeThisOuTgeminidataloggers.com | {Original Message removed}

You probably need a series resistance between OSCOUT and the XTAL (about some 100K). The crystals with 32kHz have a maximum power consumption of 1 uW. So be careful. If the Cap's are too big the quarz is destroyed thermally. Martin ;********************************************** ;** name: Martin Schaefer ** ;** company: elektronik 21 GmbH, Germany ** ;** e-mail: .....schaeferKILLspam@spam@elektronik21.de ** ;********************************************** > {Original Message removed}

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 At 01:08 AM 4/14/00 +0000, you wrote: >Today I had an 32khz XTAL startup problem, that was obviously caused by a >too small load capacitance. For the product it is essential that the >PIC always runs. Therefore I want to make further reliability tests with >the XTAL and caps. What ate the xtal specs? (Loading C, Impedance at resonance, Operating temperature etc) Are you an ISP? Tired of spam? We can help! http://www.spamwhack.com A pre-emptive strike against spam! http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -----BEGIN PGP SIGNATURE----- Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com> iQA/AwUBOPdlRIFlGDz1l6VWEQJFWACeKjnFFCzt3Ziv92TO26gAAmQFRVYAnjXs PNYDXnwgScm4cMJd9Ld89gss =VC69 -----END PGP SIGNATURE-----

<x-flowed>We use carbon composition resistors 100K in series to also introduce enough noise into the circuit to guarantee startup--also seems to significantly improve startup times from up to 20-30 seconds down to 1-2. NOTE: Carbon Comp--not metal film! Kelly At 09:18 AM 4/14/00 , you wrote: {Quote hidden}>You probably need a series resistance between OSCOUT and the XTAL (about >some 100K). The crystals with 32kHz have a maximum power consumption of 1 >uW. So be careful. If the Cap's are too big the quarz is destroyed >thermally. > >Martin > >;********************************************** >;** name: Martin Schaefer ** >;** company: elektronik 21 GmbH, Germany ** >;** e-mail: schaeferKILLspamelektronik21.de ** >;********************************************** > > > > {Original Message removed}

Just curious, What are the typical applications that people are using low freq. oscillators in the 32khz range? What's the main advantage? Low power consumption? Anything else? -Dave "William K. Borsum" <.....borsumKILLspam.....DASCOR.COM> on 04/14/2000 04:09:46 PM Please respond to pic microcontroller discussion list <EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU> To: PICLISTspam_OUTMITVMA.MIT.EDU cc: (bcc: David E Arnold/SYBASE) Subject: Re: 32khz osc problems We use carbon composition resistors 100K in series to also introduce enough noise into the circuit to guarantee startup--also seems to significantly improve startup times from up to 20-30 seconds down to 1-2. NOTE: Carbon Comp--not metal film! Kelly At 09:18 AM 4/14/00 , you wrote: {Quote hidden}>You probably need a series resistance between OSCOUT and the XTAL (about >some 100K). The crystals with 32kHz have a maximum power consumption of 1 >uW. So be careful. If the Cap's are too big the quarz is destroyed >thermally. > >Martin > >;********************************************** >;** name: Martin Schaefer ** >;** company: elektronik 21 GmbH, Germany ** >;** e-mail: @spam@schaeferKILLspamelektronik21.de ** >;********************************************** > > > > {Original Message removed}