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I'm designing a product which requires total consumption as low as possible. I came across adxl362 with ultra-low power consumption. However, I didn't figure out how to power it efficiently.

There product will have a single-cell LiPo rechargeable battery as a system power. Its voltage will be between 2.7v ~ 4.7v . A main MCU with internal LDO and DCDC, which could work between 1.8v ~ 3.6v, but is recommended to work above 3.0v due to current leakage in lower voltage , an ADXL362 could act as a motion switch .

I intent to use a buck-boost regulator to power the main system under 3.0v, i.e. main MCU. But how to drive adxl362 efficiently (preferred at 3.0v due to Vddi/o limits)? adxl362 need to work when main MCU works or not. The buck-boost regulator's quiescent current is even higher (100 ~ 200 uA) than adxl362.

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  • \$\begingroup\$ Buck Boost regulators tend to have high quiescent currents that will make the power savings of the adxl362 insignificant. You may get far better life from your battery using a linear LDO and accepting that the last few percent of your battery will be unusable as it’s voltage drops. \$\endgroup\$
    – Michael
    Commented May 1, 2018 at 23:02

1 Answer 1

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A main MCU with internal LDO and DCDC, which could work between 1.8v ~ 3.6v, but is recommended to work above 3.0v due to current leakage in lower voltage

The data sheet for the ADXL362 shows its performance at a supply of 2 volts but it will happily run at 3 volts. Current consumption is 1.8 uA at 2V and 2.7 uA at 3.3 volts. So, I'd run this device on the same regulator as the MCU.

I'm sure you can find a switcher that has lower quiescent current.

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  • \$\begingroup\$ Thank you for your answer. But I have another question on usage of switcher. I'm afraid a switcher will generate to much noise to influence adxl362. Is the noise a problem to adxl362 ? \$\endgroup\$
    – sprhawk
    Commented Mar 5, 2016 at 11:22
  • \$\begingroup\$ What about using a voltage reference as a power source to adxl362 ? \$\endgroup\$
    – sprhawk
    Commented Mar 5, 2016 at 11:27
  • \$\begingroup\$ Read the data sheet to see what it says about power supply noise - you can always use a resistor and capacitor in the power line to reduce ripple. At a current of 3 uA a 1 k resistor is going to "lose" 3 mV of supply voltage and if you took this further you might estimate that losing 100 mV of supply isn't going to be a problem - this of course means the resistor can be 33k and, in conjunction with a 10 uF cap gives a noise filter with a pass band of DC to 0.48 Hz - this should be enough to eradicate ripple induced by the switcher. \$\endgroup\$
    – Andy aka
    Commented Mar 5, 2016 at 11:30
  • \$\begingroup\$ A simple RC rolls off at 20 dB per decade and, between 0.5 Hz and (say) 50 kHz (switching ripple) there are 5 decades. This means an attenuation of about 100 dB. \$\endgroup\$
    – Andy aka
    Commented Mar 5, 2016 at 11:30

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