Electrical – Understanding IC max current in Datasheets


I'm hoping someone can help a noob out here. I've been reading a lot of data sheets of late looking for chips that will work for a small project. In short I need to drive a number of outputs (mainly LED) at 5 V 20 mA. The load is between the IC and ground (source current?) and it can't be changed. There is a ready made solution and the supplier insists it will be OK but having read the data sheet I don't think it will.

My understanding is that is has a max of 35 mA per pin, but a total of 70 mA for the IC. Am I wrong? Would really appreciate some input.

Data sheet is here:https://datasheet.octopart.com/74HCT573N,652-NXP-Semiconductors-datasheet-9888300.pdf


simulate this circuit – Schematic created using CircuitLab

Best Answer

You are not wrong. The IC has a global limit of 70 mA.

However, driving a LED at 20 mA is often unnecessary today. You should make sure that the design actually tries to do that. The current supplied to the LED depends (most likely in this case) on the current limiting resistor and the LED IV-curve. A simple indicator LED will be fine at 5 mA.