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I am interested in a microcontroller for a low power application. I have been advise to look at MSP430 or Microchip PIC microcontrollers. I also wonder if ARM-Cortex-M0 is a good choice too.

At a high level the system will have two analog sensors, few GPIO to control LED, and actuation mechanisms. The systems is intended to be powered with standard batteries.

What are the critical parameters that warrant attention in researching for a suitable low power micro controllers?

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  • $\begingroup$ Interesting question, but I feel it may be too broad for someone to give you a specific list of parameters. Depending on the complexity of the logic, you may even be able to do away with the microcontroller and simply provide a few logic gates: anything from a simple 4000 series en.wikipedia.org/wiki/4000_series chip up to a fully-programmable gate array (FPGA.) Four-function calculators and digital watches, for example, don't necessarily need microcontrollers. $\endgroup$ – dcorking Mar 6 '15 at 20:00
  • $\begingroup$ How to choose a MCU platform? Related. Broader. More general. Power issues are taken in consideration, though. $\endgroup$ – Nick Alexeev Mar 7 '15 at 1:50
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The critical parameters depends on the application. Beside Low Power, other critical parameters need to be considered. These may include code size, serial communication ports etc. Below is analysis that was preformed to choose MSP430 microcontroller. For this particular application active mode and standby mode power consumption was critical, together with the number of serial ports, and storage size.

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║ Part Number  ║ Cost  ║ Flash ║ Ram ║ USB Ram ║ Active Mode (uA/MHz) ║ LPM0 ║ LPM1 ║ LPM2 ║ LPM3 ║ LPM3.5 ║ LPM4 ║ LPM4.5 ║ UART ║
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║              ║       ║          (KB)         ║      ║ Flash  ║ Ram  ║                             uA                            ║
╠══════════════╬═══════╬═══════╦═════╦═════════╬══════╬════════╬══════╬══════╦══════╦══════╦══════╦════════╦══════╦════════╦══════╣
║ MSP430F5528  ║ $3.55 ║  128  ║  8  ║    2    ║  290 ║   460  ║  260 ║  83  ║      ║   7  ║  1.6 ║        ║  1.3 ║  0.18  ║   2  ║
╠══════════════╬═══════╬═══════╬═════╬═════════╬══════╬════════╬══════╬══════╬══════╬══════╬══════╬════════╬══════╬════════╬══════╣
║ MSP430FR5737 ║ $1.55 ║  15.5 ║  1  ║         ║  81  ║   270  ║  200 ║  175 ║      ║  61  ║  6.3 ║        ║  5.9 ║  0.32  ║   2  ║
╠══════════════╬═══════╬═══════╬═════╬═════════╬══════╬════════╬══════╬══════╬══════╬══════╬══════╬════════╬══════╬════════╬══════╣
║ MSP430FR5969 ║ $2.35 ║   63  ║  2  ║         ║  103 ║   270  ║  130 ║  80  ║  35  ║  0.9 ║  0.6 ║   0.4  ║  0.5 ║   0.2  ║   2  ║
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MSP430FR5969 has low LPM3(Standby mode) current and low Active mode current, but has less storage space.

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References:

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When low power consumption is important, you have to look at the whole picture. A microcontroller with low Joules/cycle is only one thing to look at.

A good start would be to pick a battery and micro combination where the micro can run directly from the battery over the useful voltage range of the battery. Many PIC microcontroller, for example, can run from 1.8 or 2.0 V up to 5.5 V. That nicely covers a single lithium ion cell, two or three primary "1.5 V" cells in series, etc.

Another important strategy is to let the micro sleep as much as possible. If you only need to check something once a second, then maybe you can have the micro wake up for 1 ms every second. That means you need to look at sleep current carefully. It also means you want one with a built-in RC oscillator to minimize startup time, assuming a few percent clock rate accuracy is good enough. There are lots of tradeoffs.

You didn't give enough information to have some idea of the computing power required, so we can't say what would be adequate. But in general, take a look at any Microchip PIC with the "XLP" (extra low power) feature. In particular the 16F1xxx series has some impressively low power devices.

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