[sdiy] get 5V from 12V - DC-DC converter or 7805?

[Brian Willoughby]

Unless I'm missing something, an LDO won't help unless you can reduce the input voltage.

I just read an article talking about how the efficiency of a linear regular can be increased by reducing the input voltage. However, traditional regulators require at least 3 V excess, thus you can never remove that 3 V drop. An LDO allows you to design with an input voltage that's with a fraction of a Volt of the desired output, and that helps.

In this case, we're stuck with the 12 V Eurorack standard. There will always be a 7 V drop to produce 5 V output, so an LDO does nothing to reduce that 7 V drop.

Granted, modern LDO regulators are almost as cheap as a traditional regulator, so you might as well use one. Just don't expect it to help with dissipation and loss.

Brian


On Dec 27, 2020, at 16:37, MTG <grant at musictechnologiesgroup.com> wrote:
> What about an LDO if the current draw isn't much?  I used these a long time ago:
> 
> LP2950ACZ-5.0
> 
> https://www.ti.com/store/ti/en/p/product/?p=LP2950ACZ-5.0/NOPB
> 
> GB
> 
> 
> On 12/27/2020 2:18 PM, Tony Allgood wrote:
>> The OKI-78SR-5/1.5-W36-C is pin compatible with a traditional 7805 linear regulator. The disadvantage is that it is more expensive and creates a small amount of high frequency noise that is both radiated and into the power rails. The amount of noise depends on the current draw from the +5V line, with greater currents creating more noise.
>> 
>> If the current draw is less than 100mA, I'd be tempted to use a 78M05.
>> 
>> Tony