Help this imbecile with some math - diyAudio
 Help this imbecile with some math
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 20th June 2012, 02:48 PM #1 diyAudio Member     Join Date: Feb 2004 Location: Anonymityville Help this imbecile with some math Painful as it is to admit, I have the math skills of a "no child left behind" 4th grader. Can someone please help me figure out (ok, figure out for me) what component values I need to get 750kHz from this HEF4060B as a crystal oscillator (Fig 7 in the pdf)? Thanks http://www.nxp.com/documents/data_sheet/HEF4060B.pdf
 20th June 2012, 03:17 PM #2 diyAudio Member   Join Date: Dec 2005 Location: Buenos Aires Try Rt=27 ohms, Ct= 22 nF, R2=270 ohms and C2= 220 pF. These values give f= 732 kHz
diyAudio Member

Join Date: Feb 2004
Location: Anonymityville
Quote:
 Originally Posted by willysan Try Rt=27 ohms, Ct= 22 nF, R2=270 ohms and C2= 220 pF. These values give f= 732 kHz
Ah thanks, but I'm using the circuit in Figure 7 that has an external crystal.

I think I see one thing I'm doing wrong though; the max input frequency of RS is ~8MHz for my supply voltage (5.6V) and I'm using a 12MHz crystal.

 20th June 2012, 03:45 PM #4 diyAudio Member     Join Date: Nov 2011 Location: UK In Fig 7 you will only get reliable oscillation at the frequency of the crystal. The trimmer cap will give small variation but not that much. You might be better off going for a crstal multiplication of the frequency that you require and then use a divider to get it down to where you want it. i.e 3MHz / 4 = 750 KHz
 20th June 2012, 04:06 PM #5 diyAudio Member     Join Date: Feb 2004 Location: Anonymityville The original circuit had a 6MHz crystal with an output of 375kHz taken from pin-7. In my ignorance and complete lack of understanding of the circuit I was hoping a 12MHz crystal would give double that. Maybe I'm overlooking something and one of the other outputs is already at my desired frequency?
diyAudio Member

Join Date: Oct 2003
Quote:
 Originally Posted by theAnonymous1 The original circuit had a 6MHz crystal with an output of 375kHz taken from pin-7. In my ignorance and complete lack of understanding of the circuit I was hoping a 12MHz crystal would give double that. Maybe I'm overlooking something and one of the other outputs is already at my desired frequency?
You are on the right track, this is a divider and the outputs Q3..Q13 each give a different output frequency. Basically each one is half the frequency of the previous one. The output Q3 gives 1/16 the crystal frequency (Q0 would be 1/2, Q1 1/4, Q2 1/8, Q3 1/16, etc.). Note that only 10 of the 14 "Q"s are available as outputs. You can see in Figure 2 that Q3 is connected to the output of Flip-Flop 4 (FF4), therefore the input frequency (6 MHz) has been divided by 2 four times, to give you 1/16 the input frequency. Unfortunately, the output of FF3 is not available (no Q2 output pin) so you can't get 750 kHz with 6 MHz in. For that you need to jump to a 12 MHz input, and use Q3 output.

Use the recommended components in Figure 7. Rbias is listed as 100k to 1M, and it is usually not critical, so try values in that range and pick one that works well. It is usually not necessary to have a trimmer capacitor unless you want to fine-tune the output frequency, for which you will need a very accurate, recently calibrated frequency counter. So you can just use a fixed capacitor instead of a trimmer. You may be able to find a variant of this IC that will do 12 MHz at 5 VDC.

Last edited by macboy; 20th June 2012 at 04:43 PM.

 20th June 2012, 04:59 PM #7 diyAudio Member     Join Date: Feb 2004 Location: Anonymityville Thanks Macboy, wish the datasheet was as clear as your reply. I would just up the supply voltage but the device this feeds can only tolerate a 6V input. Possible to use a resistor divider on the output?
 21st June 2012, 05:34 PM #8 diyAudio Member   Join Date: Oct 2003 Location: Ottawa, Canada A voltage divider would probably work depending on the drive capability of the output and on the input of the next device. Adding the resistance will limit current drive into the next device's input which limits slew rate, but since this is not very high frequency, you can probably get away with it. Also look at different ICs, especially 74 series, since they are almost exclusively designed for 5 V operation. The 74xx393 (e.g. 74HC393) will give you 750 kHz from 6 MHz or 12 MHz input, and will do it on 5 V.

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post wdcw Everything Else 15 1st November 2010 04:02 AM prorms Solid State 8 19th December 2006 09:48 PM poorstudent Full Range 3 22nd November 2005 07:37 AM ctardi The Lounge 3 21st June 2005 06:11 PM silverton Multi-Way 8 5th October 2003 06:49 PM

 New To Site? Need Help?

All times are GMT. The time now is 11:42 AM.