Clock Divider by 256

[JamesIbox]

Hello,
I want to divide 8Mhz clock to 31.25Khz. So I guess I need a divider by 256 IC. I haven't worked with digital logic for so long now and I can't remember which IC does this. Would you please suggest which part I can use? Thanks!
Best regards,

 

[Madcow]

Eight flip/flops in series.
Use a counter on a micro.

 

[IRstuff]

There are, or at least were, also chips that did that. Prescalers, etc.

31.25 sounds vaguely like a video application, so there may already be video chips that do that

TTFN

 

[Skogsgurra]

The 74XXy93 and 74XXy90 circuits are counters that do that. The 74HCT393 from Philips is still being produced. Cost is about 30 cents in 100+ quantities. Another circuit would be the 74HC590 from Texas Instr. It is a lot more expensive, USD 1.30 in 100+ quantities.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

You can often use something like this part, which can be driven with a crystal, but but you drive it directly. Then use it's wide division abilities.

http://pdfserv.maxim-ic.com/en/ds/DS1075.pdf

 

[felixc]

74VHC4040, a 12-stage counter chip with many intermediate divide values available. A single part would do the job. Packages from DIP to TSSOP. Price in the 50-cent range.

 

[itsmoked]

Don't forget the 4060...

http://www.fairchildsemi.com/ds/CD/CD4060BC.pdf

 

[felixc]

itsmoked, the CD series will not work with a clock source of more than 2MHz. The VHC can do in the hundreds of megs.

 

[itsmoked]

Yup. my bad!

 

[Yashu]

HCT161/3's... sync versions..

http://www.ti.com

Even in this VHDL world, I think 'they' still make them.

 

[Chuckles159]

There are other versions of the 4040 and 4060 that will run fine at 25 MHz plus.

 

[itsmoked]

Chuckles159.... A part number??

 

[jimkirk]

74HC4040:
minimum max operating frequency 24 MHz @ Vcc=4.5
minimum max operating frequency 28 MHz @ Vcc=6.0
both over Tamb -40 ~ +85 C.

Typical max operating frequencies @ 25C are 82 @Vcc=4.5
90 MHz Vcc=2, and 98 MHz @ Vcc=6.

Great 4xxx series functionality in the peppy 74HC family!

http://www.standardics.philips.com/products/hc/pdf/74hc_hct4040.pdf

Jim

 

[itsmoked]

jimkirk; Thanks a lot! I use the HC series all the time. Easily my favorite. I just never stumbled across the 4040/60.