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Are CMOS 4000 series and 74HCXX series compatible ?

H

Thread Starter

Human2

Joined Dec 22, 2017
51
One user here said that there would probalby pe problems while using
74LSXX and 74HCXX ICs together.

But will I run into any problems if I directly connect 4000 series and 74HCXX series IC's ?

Or should I buy just one type of series and stick to them ?
 
dl324

dl324

Joined Mar 30, 2015
16,916
Human2 said:
But will I run into any problems if I directly connect 4000 series and 74HCXX series IC's ?

Or should I buy just one type of series and stick to them ?
Click to expand...
The information you seek is in the datasheets if you know what to look for and how to interpret the data.

If you don't know what you're doing, you should stick with one type.
 
Papabravo

Papabravo

Joined Feb 24, 2006
21,225
Human2 said:
One user here said that there would probalby pe problems while using
74LSXX and 74HCXX ICs together.

But will I run into any problems if I directly connect 4000 series and 74HCXX series IC's ?

Or should I buy just one type of series and stick to them ?
Click to expand...
A mix of 74LSxx and 74HCTxx should work in most cases. Here the logic input thresholds have setup for Vcc = +5VDC. You should be aware the an LS output stage can sink way more current in the low (0 state), than it can source in the high (1 state). Also the HCT gates inputs are OK with pullup and pulldown resistors. Pulldown resistors on an LS gate are a very bad idea. LS gar inputs source current and will develop a voltage on a pulldown resistor that may exceed the logic threshold.

You can mix 4000 series and 74HC devices if they both use a Vcc of +5VDC. The drive capability and the maximum frequency of the 4000 series could be an issue in some cases. You need to learn to read datasheets and extract the relevant information from them.
 
Audioguru

Audioguru

Joined Dec 20, 2007
11,248
I use CD4xxx ICs with supplies up to 18V and with fairly low output currents. At 5V a CD4017 can barely light an LED even without a current-limiting resistor. At 12V it overheats when driving an LED so it needs a current-limiting resistor.

I use 74HC4017 ICs with 5V to brightly light LEDs with current-limiting resistors. The 74HC4017 ICs are reliably driven with signals from CD4xxx ICs powered from 5V.
 
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