Driving a 4V chip with an HC logic chip

[panfilero]

Hello,

I have an HC logic IC, that outputs about 5V, and I need that to be turned into 4V and wired into the input of another IC. Can I just put a resistor divider in the circuit to knock down the voltage, or is that not a good way to interface two logic IC's from different families. So I need a cap in there or anything, or just a divider, thanks!

 

[Diver300]

A divider will usually work fine.

You can just run the HC device on 4 V, and there are various ICs, such as the 74LVC1G04, that will work fine with an input voltage that is larger than the supply voltage.

You have to look carefully at the specifications for an IC. Some will have Vin(max) = Vcc + 0.5 V or similar. They will not be happy with a larger input voltage than the supply, if the difference is more than 0.5 V.

Others will say Vin(max) = 6 V or similar. There is no reference to Vcc for that so it is fine to connect the input to 5 V even when the IC has no power.

 

[MikeMl]

What is the logic that the HC is driving? That will determine what is needed.

 

[panfilero]

Thanks for the responses, I'm not really driving another logic IC, I'm actually using an HC chip (an OR gate) to drive an analog switch... I can't power my HC chip with 4V due to the rest of the circuit, but my analog switch requires between 2.6-4.3V to operate... if there's not problem with stickin a divider at the output of the NAND gate, then I'll go that route. much thanks!

The OR gate: https://www.electro-tech-online.com/custompdfs/2011/02/DS005132.pdf
The Analog Switch: https://www.electro-tech-online.com/custompdfs/2011/02/FSA2367.pdf