Tell me more x
, there is a new speed test available. Give it a try, leave feedback!
dslreports logo
 
    All Forums Hot Topics Gallery
spc

spacer

Search Topic:
uniqs
1012
share rss forum feed

SipSizzurp
Fo' Shizzle
Premium
join:2005-12-28
Houston, TX
kudos:4

Frequency division with Binary counter

I have put together a simple circuit using a CD4024BC Binary counter ;
»www.jameco.com/webapp/wc ··· DownView

I am feeding it a square wave input that has a 90% duty cycle, but the divided outputs of the CD4024B are at a 50% duty cycle. Could somebody give me some ideas on how to make a frequency divider with outputs that have the same duty cycle as the input ?

For this project I only need two outputs, Input /2 and Input /4, not all 7 stages that this chip supplies. I'm thinking I may need a different style of counter but am not sure which.


shdesigns
Powered By Infinite Improbabilty Drive
Premium
join:2000-12-01
Stone Mountain, GA
kudos:1
You can do 75% for the /2 and 87.5% with the /4 with simple logic.

Are you trying to match the duty cycle with the input duty constant or does it vary?

SipSizzurp
Fo' Shizzle
Premium
join:2005-12-28
Houston, TX
kudos:4

1 edit
The input duty cycle will be constant. I may want to adjust it periodically, so if I could have the output track the input duty cycle that would be ideal.

I was also thinking about gating the output with an AND gate, with one of the AND inputs being the original input, but I think that could still leave an un-true output towards the end of the cycle. Still brain storming.

If it makes any difference, the signal that I want to work with will be in the range of 3 - 15 % duty cycle, not the 90 that I am testing the circuit with.


cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to SipSizzurp
You can use a decade counter to preserve the 90% duty cycle.
As a general rule for each division stage you can get a k/N duty cycle where N is the division factor of a stage and k=1...N.
With a binary counter you'll only achieve duty factors that are in the form of sums of 1/2, 1/4, 1/8, 1/16 (ex 1/2 + 1/8 +1/16+ 1/64)

SipSizzurp
Fo' Shizzle
Premium
join:2005-12-28
Houston, TX
kudos:4

1 edit
Thanks for the ideas. I'll check into a decade counter. This got me to analysing exactly what I want the 3 final signals to be, and now I'm hunting up some timing diagram software.

This is for a harmonic amplification project so I want all 3 signals to be in phase with each other, which is why I thought using a counter to divide the fastest signal down would be the best approach.