How to determine power needed for an IC

Question

I want to use solar cells as power source. Let's say I am using 12 cells, and that gives me 43W of power. I will use this power source to power multiple ICs, such as this current sensor. How can I determine how much power the sensor consumes? I want to know this because if I want use multiple of them or any other ICs, I may want to make sure that my power source has enough power.

I am very new to schematic design. I wonder if power is a must thing that we need to think about while doing schematic design.

Answer 1

You can read the data sheet how much the sensor chip itself requires for operation. It's commonly called supply current or quiescent current.

And strictly speaking, you really don't consider the power consumption of chips at the schematic design stage any more. Those considerations should be done at a step that happens before starting the schematic design, where you decide what chips you have to use and how to power them, and then start with the schematics when you have determined what parts to use and how to power them, and what kind of connections they need to work and perform their function.

Answer 2

Chip data sheets should give the power (or current) consumption of the chips, at least in some ideal condition. Then you can start from there and estimate how power the chip will really consume.

For most chips, the current consumption listed will be with the chip in operation, but with no loads on the output pins. However, any good data sheet will list the conditions under which a given parameter is specified -- so if, for instance, the chip will only work properly with some output pins loaded, the manufacturer should (and maybe will) give you a power figure for that condition.

Then you have to add in any load that you're putting on the chip -- i.e., if you're driving something with an amplifier, the current to do that is on top of the amplifier's quiescent current. Similarly, if it's some logic circuit, then any loads you put on the output pins (other chips, LEDs for indicator lights, etc.) will add to the current consumption.

Generally if you're serious about estimating power consumption, you'll end up with a giant spreadsheet that lists each component, it's quiescent current, any additional current draw you're causing it to have, and it's overall current. Then you sum up that "overall current" and you have an answer.