# Power dissipation in MCU

I am posting a screen shot of the abs max rating of the LPC43xx microcontroller. It states that the total power dissipation of the package is 1.5W. I am assuming that the total power dissipation means the power dissipated when all the peripherals and all working inside the MCU. Supposing I have only the I2C working how much would the MCU dissipate in terms of power. Also this chip has regulator power supply and I/O voltage supply.

Should I incorporate the power contribution from both and sum it up, so Preg+PI/O?

Will the total power dissipated be the power of the above + PI2C ?

The maximum power dissipation is a rating of how much power the package can physically dissipate. How the MCU ends up drawing that much power is another matter; for instance, it could be simply a lot of GPIO pins each driving substantial output current.

If you want to compute actual power consumption, you should look at the relevant figures in table 10 for power consumption (for instance, IDD(REG)(3V3)), the graphs in figures 11 through 19, and the peripheral power consumption figures in 10.2. Sum up the relevant figures and multiply by the operating voltage to get a figure in watts.

• It should be noted that total power consuption for a microcontroller is dependent on so many factors, that any calculation should be regarded as a half-assed guess. Measurements must be taken in the actual use cases. Commented Jul 15, 2015 at 17:05
• But just to analyze it theoretically, how do I start off in this case ? Should I merely add up power of all the peripherals ? What of the arm core ? The table shows M0 core as 6mAmps at 97MHz. So I should scale it up to get a value at 204MHz. That's it ? Then sum that to the individual peripherals power ? Commented Jul 15, 2015 at 17:40
• @VinodKaruvat It doesn't scale linearly with an intercept at 0 - but the datasheet has a graph showing the power consumption over speed. And yes, then just add the peripherals. Commented Jul 16, 2015 at 8:32

No. That section of the data sheet is the absolute maximum that you can allow the chip to dissipate or it may be damaged. It does not imply that the chip will take that much. It is mainly dependent on package design.

As you say in your comment you need to add up the consumption of all of the various parts within the chip to determine the actual dissipation.

The core power consumption will depend upon the code that is being executed. You can scale the power with frequency as you say but if there is only one I2C peripheral to service the processor will probably spend most of its time in a wait for interrupt loop where it requires very little power, even if the clock frequency is high. The example you mention is probably for a tight loop where the processor is executing as fast as it can.