I'm looking to use some of the 4000 series logic chips at around 5MHz (mainly the 4017, AND gates and inverters) for a dot-matrix LED controller. I was wondering if these chips will work efficiently at these speeds? If so, what are their limits?

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hi,
Get the data sheet for the HEF4017 from: Datasheet Archive - Free Datasheet Search Engine :: PDF Datasheets :: Data Sheet :: Datasheet :: Application Note : çš„å�‚æ•° : 规æ*¼ä¹¦ : 技术资料 : ë�°ì�´í„°ì‹œíŠ¸ : データ・シート : Fiche technique : Datenblatt : опиÑ�ание

Look at the bottom of page #4.

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Eric " Good enough is Perfect "
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The CD4017 is not likely to work well, if at all, at 5MHz. 74HC/HCT4017 works to at least 20MHz.

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Ron

 

The max recommended clock for a Texas Instruments CD4017 is 2.5MHz with a 5V supply and 5MHz with a 10V supply.

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Uncle $crooge

 

The National CD4017 datasheet says the maximum clock frequency at Vcc=10V is 5MHz typical, 2.5MHz minimum.

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Ron

 

Looking at the datasheets, it would happily run at 5.5MHz at 15V. I was just wondering if anyone has had any experience running these chips are high frequency. If, so, what to look out for?

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At 15V and at 5.5MHz then some of the ordinary Cmos logic chips might be hot.
They can't slew that fast so their Mosfets spend a lot of time in the linear region charging and discharging internal capacitance and getting hot, instead of being saturated where they are designed to be cool.

74HCxxxx high-speed-Cmos switch much quicker and have a lower supply voltage so they would be cool.

My two-cents, I haven't tried it.

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Uncle $crooge

 

Yes, I'll go with the 74HC series. Thanks for the advice.

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Sorry to bump again but I am not worried about the 74HC04. Will not be able to sink enough current for my application.

I need it to sink about 40mA (on the output pins). I'm assuming I will need to use a transistor to do the job, could anyone suggest to me how I could connect it up? I've attached a schematic to show how it's connected at the moment. The second attachment is just my idea.

Attached Thumbnails

   

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The max allowed output current from a 74HCxx is 25mA and the max for a package is 50mA. Two inverters can be paralleled to drive 40mA. The LEDs need series current-limiting resistors. A single inverter can drive a PNP emitter-follower transistor and the LEDs still need series current-limiting resistors.

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Uncle $crooge

 

AG's right here, but parallel more than just two together. Our standard practice was to always use four; it's a bit more wiring but easier on the gates that way. Max current still 50mA...

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Go Trojans!

 

A single 74HCxx inverter or gate will try to make an output current of 60mA. Two in parallel will drive 40mA into LEDs perfectly.

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Uncle $crooge

 

Unfortuantly, because of size and cost requirements I cannot use more than one inverter per set of LEDs. Can anyone suggest to me a good transistor that would switch at around 1MHz? And recommend a good way to wire it?

Attached Thumbnails

 

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when you post that reply, im just kidding.

 

One 74HC04 costs only $.47US at Digikey today. It has has six inverters inside. The inverter can switch quickly because its output is push-pull. A single transistor turns off slowly but a complimentary push pull pair can switch quickly.

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Uncle $crooge

 

Digi-Key - 296-4024-5-ND (Texas Instruments - SN74ABT540N)

Can go quite fast and pull 128mA to gnd on EVERY pin