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I'm making a portable device (well not really portable, but intended to be set up away from mains power) powered by AA batteries. I need a stable VCC as I have displays that I don't want the brightness to change on (I'm also considering using VCC as a reference, see this question). I need the VCC to remain stable as the batteries drain, atleast to a certain extent (say until the batteries are atleast 80% depleted).

I'm thinking I'll use LDO(s) to provide power, as none of the circuits should consume that much power so I won't need anything more bulky. Is there any better solution for this kind of device, or is it fine to use LDO(s)?

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  • \$\begingroup\$ We don't know anything about what you are powering, but almost anything is better than linear regulators. The best solution depends on what voltages you have on inputs and outputs and what currents you need. Maybe there is also better solution than AA batteries? \$\endgroup\$
    – Justme
    Mar 29 at 12:19
  • \$\begingroup\$ Basically all I'm powering is some IR LEDs, some 7-segment displays and some logic chips. The total power consumption is 2A tops. \$\endgroup\$ Mar 29 at 12:32
  • \$\begingroup\$ 2A sounds a lot for a bit of logic and some LEDs, but if that is an accurate assessment, you'll almost definitely want a switch-mode power supply. The kind of which depends on the actual voltages and batteries involved. Please answer all the questions Justme asked! \$\endgroup\$ Mar 29 at 12:41
  • \$\begingroup\$ @Justme I don't really know if anything but AA batteries is suitable, as it must be battery powered, it must be compact, and it must be able to be stored in a hot place for a long time without checks. The input voltage so to say is 1.5V, going down to about 1.1V where I stop caring about getting energy out of the battery. In terms of outputs, I need to produce a 5V VCC with noise less than 100mV either direction, and as said around 2A peak current. \$\endgroup\$ Mar 29 at 12:58
  • \$\begingroup\$ @SteamRanger the requirements you list (high energy density, long storage live, maintenance free) all say that AA are not the right choice. If your output voltage is higher than your battery voltage, then linear regulators are simply impossible to use, as they can only reduce, not increase voltage, so that settles that. 100 mV is not a complicated requirement to achieve. \$\endgroup\$ Mar 29 at 13:16

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Essentially, you have the choice between switching regulators and linear regulators with LDOs being just a flavor of linear regulators.

If efficiency is a concern, you maybe want to use a switching regulator. Also switching regulators usually cover a wider input voltage range than linear regulators. With the right topology, the input voltage can even drop below Vcc.

Linear regulators on the other hand are usually simpler to use and less noisy. But the input voltage always needs to be above Vcc. LDOs can have their input a little closer to Vcc than conventional linear regulators. But LDOs can also have a tendency to become unstable under certain circumstances.

Considering your circuit is drawing 2 A and you need Vcc stable "until the batteries are at least 80% depleted" a switching regulator appears to be the more favorable option.

If you used a linear regulator, the input voltage just being 1 V above Vcc would cause 2 Watts of power dissipation inside the regulator at 2 A. That would heat up the linear regulator quite a bit.

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  • \$\begingroup\$ I was unaware of the existence of switching regulators (I'm a bit new to electronics incase you can't tell), thanks, they suit my needs well. I found one with 150mV noise, which is just fine. \$\endgroup\$ Mar 29 at 13:39

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