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If I have a power supply that is feeding a fully integrated voltage regulator(Lets call it VR) and so on the VR is feeding a chip.

My goal is to calculating the static icc of the chip but I dont have a physical access to that line.

I can only meassure the static icc on the power supply.

I know that the VR have some power losses so How can I calculate it? Thanks

schematic

simulate this circuit – Schematic created using CircuitLab

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2 Answers 2

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By knowing the part number of the regulator you can generally use the datasheet to work out what the current consumed by it is, e.g. something like 7805 has a static current based on the input voltage,

enter image description here Image source

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It depends on the regulator how much current the regulator uses internally.

Some linear regulators draw more-or-less constant current for a fixed input voltage regardless of output load current. So you can just subtract the quiescent current from the regulator input current and get the approximate load current. You can expect Iq for the regulator to vary with temperature, at least, and from unit-to-unit.

Some older linear regulators draw significantly more current as the load increases.

Switching regulators may have an optimum efficiency point and different operating modes (such as for when the output load is very light), making it fairly complex, especially if the load current varies over a wide range. They do not have the simple approximate relationship of Iin = Iq + Iload, of course.

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  • \$\begingroup\$ Are there any formula examples of modeling such current? \$\endgroup\$ May 6, 2020 at 6:14
  • \$\begingroup\$ If you have a SPICE model you can model the typical input vs. output current under similar conditions to your circuit. LTspice is free and most manufacturers supply models. \$\endgroup\$ May 6, 2020 at 6:24

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