0
\$\begingroup\$

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.

\$\endgroup\$
1
  • \$\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
    May 1, 2018 at 23:02

1 Answer 1

Reset to default
1
\$\begingroup\$

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.

\$\endgroup\$
4
  • \$\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
    Mar 5, 2016 at 11:22
  • \$\begingroup\$ What about using a voltage reference as a power source to adxl362 ? \$\endgroup\$
    – sprhawk
    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
    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
    Mar 5, 2016 at 11:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.