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[General] Measuring miniscule currents during microcontroller low power modes

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kender

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Folks,

Out there is there a good app note on tools and techniques for measuring low power microcontroller modes? How does one usually go about measuring the consumption at the low power modes? uA levels.

Imagine the situation when sleep current is in single-digit uA (micro), and active current peaks at tens of mA (milli). Is there a current measurement technique that can cover such range (4 orders of magnitude) without obstructing the operation of the DUT?

I can think of having a bank of different current sense resistors in parallel. They would have to be manually commutated depending on the power consumption mode. But that means that the power consumption mode can't change rapidly, otherwise manual commutation will not be able to keep pace.

My gut feeling tells me that the MSP430 people could have come up with an app note like that. They advertise how low their power consumption is; they might as well tell us how to verify our own power consumption. But I haven't found a right app note yet.

I'd hate to reinvent the wheel, unless I absolutely must. Any suggestion, insight or reference is really appreciated!

Cheers,
- Nick
 

A multi meter with a low burden voltage. Try EEVBlog's uCurrent.

You could use a high side current sense amplifier, but that is re-inventing the wheel.
 

The solution depends on what you want to measure. Either average current including the µC activity periods or sleep current only. Average current can be best measured with a RC shunt circuit, to measure the sleep current, a schottky diode + shunt parallel circuit can do.
 

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