I'm using the NXP LPC1100 series CPU, which is their most low-power Cortex M0 offering. However, in the datasheet it states that under the most optimal conditions (sleep-mode + all peripherals disabled) it still uses 6 mA, and my measurements confirm this.

How can it be that my smartphone (which has a 1Ghz CPU, and a lot of active peripherals) uses only 3 mA while in standby, when this 48Mhz Cortex uses so much more when not even active?

  • 1
    \$\begingroup\$ To my knowledge, no smartphone uses an ARM Cortex-M0. Also, there are no 1+ GHz M0's. \$\endgroup\$
    – user3624
    Jan 5 '13 at 4:49
  • \$\begingroup\$ @DavidKessner Ofcourse I'm aware my smartphone has a different CPU (Snapdragon), but Im just wondering how its possible that it beats the very simple Cortex-M0. \$\endgroup\$
    – Muis
    Jan 5 '13 at 11:45
  • \$\begingroup\$ For me, battery life is one of the most important features of my phone smart/dumb. I'm sure the vendors are aware of that people think this and optimize that feature. I suspect the chipsets they are using allow sleep modes and disabling subsystems well under a mAmp. \$\endgroup\$
    – kenny
    Jan 5 '13 at 12:34
  • \$\begingroup\$ Just placing a bounty isn't going to do much good. Try some experiments with the lower power sleep modes on the hardware and post some further details if you want additional assistance - right now the ball is in your court and most probably thought the question abandoned. \$\endgroup\$ Jan 15 '13 at 22:08
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    \$\begingroup\$ That's already been answered - most of the smartphone chip is suspended, only specialized blocks having to do with the radio and timers keep running - your impression that "apps" continue to run during the low power suspend is mistaken. And your question still contains a flawed claim that 6 ma is best case for the LPC - in actuality, that is the worst of the 3 low power modes, the other two of which are a thousand times better. \$\endgroup\$ Jan 16 '13 at 3:26

You aren't entering the lowest power mode. Take a look at AN11027.

Regular sleep mode yields single digit milliamp consumption, as you have seen.

Deep sleep mode is in the single digit micro amp range.

Deep power down is a few hundred nanoamps.

Also be careful of things in the surrounding circuit which can steal power (or even supply it, invalidating your measurements). These could include connected communication or programming interfaces and pullup/pulldown resistors working against an asserted signal.

  • \$\begingroup\$ I know about deep-sleep mode, but it seems unusable for my project, because in deep-sleep the clock is very inaccurate (40%) and I need to sample data at exactly 256 Hz. I was just wondering how my smartphone can be more power-efficient, because it also cannot use deep-sleep (I assume), since there are apps running in the background. \$\endgroup\$
    – Muis
    Jan 5 '13 at 11:48
  • \$\begingroup\$ You may be able to use an external watch crystal for the low speed oscillator, though sampling data perfectly in sleep mode is a lot to ask. A smartphone has all its components engineered to a goal - apps do not run while it is asleep (which is a stage beyond screen off), but the mobile radio and various timers do. \$\endgroup\$ Jan 5 '13 at 14:38

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