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I've found that more and more ICs have possibility to use 1V8 power rail to optimize power consumption. I'd like to know if it's still good to use LDOs in low power applications where common 3.7v batteries are involved.

From 4.2/3.5V to 1V8 instead of 3V3 will result in higher drop. Would be more convenient use a switching regulator?

I can put some data as example like a 3.7V LiPo 150mAh and an LDO like LP2985 or switching like DIO6015 . Hypothetical power consumption of 2 mAh active and 1 uAh sleep.

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  • \$\begingroup\$ Combined voltage regulators do exist that run in switching mode when loaded and in linear mode when the load is very light. But for 2ma max load I am not sure you can find one. \$\endgroup\$
    – fraxinus
    Nov 9, 2022 at 16:00
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    \$\begingroup\$ For such a light load im sure a switcher would not make sense \$\endgroup\$
    – Linkyyy
    Nov 9, 2022 at 16:10
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    \$\begingroup\$ Power consumption isn't measured in mAh and neither is current. \$\endgroup\$
    – Andy aka
    Nov 9, 2022 at 17:08
  • \$\begingroup\$ Is the power consumption any different at a higher voltage? \$\endgroup\$ Nov 9, 2022 at 18:43

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It's seldom more convenient to use a switching regulator in a low-power application where an LDO will do the job without trouble. 2mA * (3.7-1.8) ~= 4mW regulator dissipation, so you're definitely in low-power territory. If you must save energy then it might be necessary to consider it. If the application spends most of its time in the 1uA state, then an LDO will probably be not much different in efficiency as well.

Here are a couple of datasheets you can look at, and then do your own research based on the details of your application as to what applicable parts are on offer and actually available:

Ultra-low Iq LDO:

enter image description here

Ultra-low Iq switching regulator (note that the efficiency is not shown for Vn < 3.6V) : enter image description here

If the application spends 99% of the time in the sleep mode and 1% active, then the LDO solution draws an average of 0.99\$\cdot\$2uA + 0.01\$\cdot\$2mA = 22uA.

The switching solution draws 0.99\$\cdot\$1.8uA + 0.01\$\cdot\$1.2mA = 14uA, based on 27% efficiency/80% efficiency.

So this particular switching regulator comes out on top, but it may not be significant, depending on the self-discharge current of your LiPo cell. An 18650 cell has a self-discharge current in the 40uA range (more during the first 24h), so the comparison would be between 54uA and 62uA, not particularly significant.

Since this particular switching regulator won't work down to the 'fully discharged' voltage of a typical LiPo battery, it's probably not appropriate in your application but it does give some comparison. Also, read the datasheet on inductor selection and layout for the switching regulator before deciding which is more convenient. The only critical thing with LDOs is ensuring the capacitors are correct.

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