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I have a MCU that can be put into a sleep mode that pulls only 5uA, but my voltage regulator has a quiescent current of 50uA datasheet Normally the MCU pulls 300mA or so, but I am wondering what will happen to the voltage regulator if the MCU goes to sleep. Will it cease to produce any current on its output?

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  • \$\begingroup\$ The output voltage appears only to be specified with a minimum load current of 1 mA and anything less than this may cause problems with this device. You need to check this out. \$\endgroup\$
    – Andy aka
    Apr 5 at 14:01
  • \$\begingroup\$ @Andyaka that’s just a standard idle load which reduces noise and used to measure Vout stability vs temp which is pretty good 0.1% that will not matter when ADC is asleep. \$\endgroup\$ Apr 5 at 18:05
  • \$\begingroup\$ So, are you telling the OP that he needn't worry about my concern in this matter @TonyStewartEE75 \$\endgroup\$
    – Andy aka
    Apr 5 at 18:08
  • \$\begingroup\$ That’s correct. There are also specs for 0A load and no warnings about no load. FWIW @Andyaka \$\endgroup\$ Apr 5 at 19:39
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what will happen to the voltage regulator if the MCU goes to sleep. Will it cease to produce any current on its output?

It will provide the 5uA demanded by the MCU at the specified voltage.

Quiescent current will flow from the input voltage source to the "GND" pin of the regulator.

my voltage regulator has a quiescent current of 50uA

Also note that this current varies (a lot) according to the load and temperature:

enter image description here

The IC has a shutdown pin, but it seems to not be an option for your application since the "sleep mode" of the MCU is being used (instead of a reset).

enter image description here

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    \$\begingroup\$ Note that, though it should still work fine, this does mean that you're wasting a significant fraction of the power while the IC is in sleep mode. You may want to consider a voltage regulator designed for low-power applications if you plan to use sleep mode a lot (and no, that doesn't necessarily mean a switching converter! They are more efficient than linear regulators, but have typically far higher quiescent current.) \$\endgroup\$
    – Hearth
    Apr 5 at 14:43
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Quiescent current is the current needed by the regulator itself. Load current of 0mA is allowable according to specs.

So nothing interesting happens if the MCU suddenly reduces consumption from 300mA to 5uA or 0uA.

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Yes in sleep mode the output it will only supply 5uA but quiescent internal remains the same 50uA or 16 uA shutdown.

If this is not acceptable, then what specs are acceptable? You may need a better discrete design.

I do not see any LDO’s that are better for Iq and IMAX but it is possible with a discrete design of mixed technology. HEXFET and CMOS linear.

correction:

Sansen has a 1uA=Iq with a IMAX of 3A 5V

https://www.digikey.ca/en/products/detail/sanken/SI-3011ZF-TL/4175711

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