Unstable Current Consumption

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ali.sakir

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Hi,

We have designed a PCB that includes a microcontroller from Texas Instruments and want to determine how much energy consume each element. To determine microcontrollers power consumption, we have only mounted regulator and microcontroller. We were changing firmware to monitor power modes of microcontroller.

While doing this cycle, we realized that current consumption of the circuit is changing dramatically despite no firmware or hardware alteration. We measured current consumption of the circuit and repeated it again after a day. Although no changing on the PCB and firmware, current consumption is increased 30%.

What could cause this rising current consumption?

Thanks in advance
 

Wait, first you say your were changing firmware, then you say there was no firmware change. Which is it? Is the board running continuously for a day, or did you turn it on, measure the current, turn it off for a day and then do it again?

That confusion aside, I would suspect that something is heating up. As this device heats up, it draws more current. Maybe you've got a tantalum cap mounted backwards, something like that. Maybe something is oscillating; does the regulator have proper capacitors on the input and output? Have you measured voltages in your circuit? Have you looked at things with a scope?
 

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