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CD4026 IC become very hot

unclejed613

Well-Known Member
Most Helpful Member
i can see the tool marks on the pins of the top one, the TI logo and printing are better defined, and the bottom one has some kind of oxidation on the pins. the circle edges on the right end of the top one are well defined and sharp... the bottom one also looks as if it's been sandblasted...
 

granddad

Well-Known Member
My 2 cents worth.. CD4026 needs an output driver. or you will kill the silicon , whatever.... Maximun Source or Sink is 6.8mA with a 13.5v supply ..
4026.jpg

{ just because the circuit is on the internet , don't make it correct..}
 
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Fintek

New Member
It does not need anything beyond some resistors between the output pins and the display, which may be optional. The TI chips work fine using the online schematic. The other chips were definitely bad, one exploded during power up at 5v. I've ran the circuit now for a while, and it stays at room temperature.
 

granddad

Well-Known Member
I suggest for reliable operation, follow the TI data sheet for driving leds .
led4026.jpg


The ULN2803 is ideal for such an application
The ULN2803A device is a 50 V, 500 mA Darlington transistor array. The device consists of eight NPN Darlington pairs that feature high- voltage outputs with common-cathode clamp diodes for switching inductive loads.The collector-current rating of each Darlington pair is 500 mA. The Darlington pairs may be connected in parallel for higher current capability .Applications include relay drivers, hammer drivers, lamp drivers, display drivers (LED and gas discharge), line drivers, and logic buffers.TheULN2803A device has 2.7-kΩ series base resistor for each Darlington pair for operation directly with TTL or 5-V CMOSdevices
 
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Fintek

New Member
Remember, these specs were written in the 1970's, LEDS are a lot more efficient now. I'm pulling less than 10ma per segment, I think a Darlington transistor array may be overkill. Even the transistor arrays they suggest in the spec sheet (ca3081-82) are for high current applications. Now, if you are making some high intensity or billboard display, you will definitely have to add some more parts. But for a single digit counter, it'll be fine with just resistors. Plus, to conserve power, I'm not even keeping the display on all the time. It's only on when a "check" button is pressed to make the display enable pin high.
 

resr1286

New Member
I got the same fake CD4026 chips from aliexpress with the same 81A5YTK date code. It is actually a CD4017._
 

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