National is not making these chips anymore but has moved its logic line to Fairchild again. Hence the corresponding datasheet for your device would be the one on
http://www.fairchildsemi.com/pf/MM/MM74HC4046.html which states a significantly lower "maximum operating frequency" for the VCO, and not at all a "maximum center frequency"! Uwe. BOD> Yes, I was breadboarding the circuit. Out of curiosity, I measured the BOD> capacitance between adjacent terminals and found from 5 to 7 pf of BOD> capacitance. I guess I'll have to make a demonstration circuit for myself BOD> on a PCB. Hey, I could use both the MM74HC4046 and LMC555 in the same BOD> circuit, using the LMC555 as the timebase! BOD> I don't recall that there's anything wrong with tying the VCOin pin to Vcc BOD> as a convenient way to generate the max. VCOout, it's just that the response BOD> is only linear .9V to 1.1V from each rail. BOD> My chip is a National MM74HC4046N. BOD> Brad BOD> ----- Original Message ----- BOD> To: "Multiple recipients of list CHIPDIR-L" <[EMAIL PROTECTED]> BOD> Sent: Wednesday, August 11, 2004 1:00 PM >> I think, it's not allowed to just tie the vco input pin logical "high" >> (Vcc). >> Use some other (lower) voltage (e. g. Vcc/2). >> The vco has its input voltage range, and that doesn't go from rail to BOD> rail. >> I don't know, what will happen if the input is beyond its limits, but this >> could be the problem. >> And which manufacturer is the chip from? >> >> Steffen Maisch >> >> -- >> Author: Steffen Maisch >> INET: [EMAIL PROTECTED] >> -- Author: Uwe Zimmermann INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
