Sourcing with CMOS Chip, Ioh/Iol

[czwalga00gt]

So, I'm trying to power a diode/resistor that requires 15mA. I want the output of a 4 input NOR gate to power this. I guess it's been forever since I've dealt with CMOS logic. I was looking for a simple output current max.


This was the chip I was looking at.... 5v VDD/inputs. I was expecting to get a 5v output when conditions are high and source the diode. The Ioh is -1mA min. Doesn't seem to list the max in the datasheets. Am I way out in left field trying to do this?

CD4002BE Texas Instruments | Mouser

CD4002BE Texas Instruments Logic Gates Dual 4-Input datasheet, inventory, & pricing.

www.mouser.com

 

[rjenkinsgb]

1mA is the maximum current it can be guaranteed to source without the output voltage dropping below (or significantly below)whatever the Voh value is for that supply voltage. At higher currents, the output voltage will progressively fall.

The data sheet gives typical and worst case Voh vs. output source current for various supply voltages; figures 8 & 9 on page three.

With a 5V supply, at worst case the output is near zero with just a 2.5mA current.

To switch higher currents at 5V from a CMOS gate, you ideally need either a darlington driver array or some P-channel logic level FETs.

 

[audioguru]

Ordinary old CD4xxxx Cmos is designed for low power. Its output is designed to drive the no-current input of another Cmos gate and charge stray capacitance. The graph in its datasheet shows that with a supply that is only 5V then the worst case output sourcing current into a dead short is 2.5mA and is less current if the load has some resistance.

A 74HC4002 will have much higher output current but it will not have an output as high as 5V at 15mA, it will be about 1V.