# How to choose the Best DC-DC converter?

#### oridroo

Joined Feb 5, 2012
27
Hi,
I need to choose a 5-3.3V DC-DC converter.
I have been getting several products.
So please suggest how can I determine the Best one among them?
What are the characteristics I should be looking for into the Datasheets?

Regards

#### ci139

Joined Jul 11, 2016
1,696
"best" is undefined

#### oridroo

Joined Feb 5, 2012
27

#### bertus

Joined Apr 5, 2008
21,255
Hello,

What criteria are important for choosing the DC-DC converter?
Is it efficiency?
Is it noise?
Is it size?

Bertus

#### oridroo

Joined Feb 5, 2012
27
Hello,

What criteria are important for choosing the DC-DC converter?
Is it efficiency?
Is it noise?
Is it size?

Bertus
I'm looking for smoother power supply basically. So is there any way to determine one depending on the given info in the datasheet thus I can test it out?
Thanks

#### bertus

Joined Apr 5, 2008
21,255
Hello,

Switching regulators will always make noise.
They are more efficient as linear regulators.
Linear regulators do not create extra noise.
They are less efficient as switching regulators.
For the voltage difference you show, a LDO regulator will work.
The LD1117 will work upto 800 mA.
For higher currents look at the LT1083,LT1084 or LT1085.

Keep in mind that linear regulators will need cooling.

Bertus

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#### oridroo

Joined Feb 5, 2012
27
Hello,

Switching regulators will always make noise.
They are more efficient as linear regulators.
Linear regulators do not create extra noise.
They are less efficient as switching regulators.
For the voltage difference you show, a LDO regulator will work.
The LD1117 will work upto 800 mA.
For higher currents look at the LT1083,LT1084 or LT1085.

Keep in mind that linear regulators will need cooling.

Bertus
Thanks a lot. I'll check it out.

#### ci139

Joined Jul 11, 2016
1,696
search something like https://www.google.com/search?q="step+down"+"low+noise"+92%+DC+DC+3.3V

depending on I/O power and voltage the reasonble MAX conversion efficiencies vary from 87 to 98 % .. .. 88 to 92 are somewhat common (achievable with relatively simple/robust topologies) . . . $$\leftarrow$$ "predicting" the conversion efficiency in your search just might filter out some "noise" in the results

#### Papabravo

Joined Feb 24, 2006
15,520
Hi,
I need to choose a 5-3.3V DC-DC converter.
I have been getting several products.
So please suggest how can I determine the Best one among them?
What are the characteristics I should be looking for into the Datasheets?

Regards
In order to make the kind of value judgement that you asked for you must define your requirements. Once your requirements are defined we can do two things:
1. Evaluate the alternatives
2. Tell you what "done" means
Without a set of requirements, everything else is just idle speculation and storytelling.

Last edited:

#### dl324

Joined Mar 30, 2015
12,684
So please suggest how can I determine the Best one among them?
What are the characteristics I should be looking for into the Datasheets?
Start by defining your requirements.
1. You say you want low noise? How low? Why?
2. What about area?
3. What about cost?
4. What about efficiency?
5. What power does the load require?
6. What is the load?
7. What is the power source?
8. If source is a battery, what is the runtime expectation?
9. Etc.

#### oridroo

Joined Feb 5, 2012
27
Start by defining your requirements.
1. You say you want low noise? How low? Why?
2. What about area?
3. What about cost?
4. What about efficiency?
5. What power does the load require?
6. What is the load?
7. What is the power source?
8. If source is a battery, what is the runtime expectation?
9. Etc.
Hi Dennis,
Thanks for the organised questions which helped me to be more specific.

1. I am going to use the converter to supply a microprocessor (Pycom LoPY4). As I'm using the built in board, I observed the power supply to the chip is having some noises. I'm suspecting it could be one of the reasons that I'm getting noises in the output as well. So I want to try a smoother power supply to compare the output.
2. The smaller the area is, the better as I will be incorporating the converter on a 75*25 mm board (most likely).
3. Generally the higher efficiency is expected but as 'ci139' mentioned in earlier post that for simpler devices, the efficiency ranges in between 88-92%.
4. The maximum power would be consumed around 1.3W although it's theoretical maximum. Practically, it would be around 0.4 W
5. The load is the microprocessor.
6. The power sources are mini solar panel (1W) and a 3.7 V, 2500 mAh Li-ion battery. Right now I'm powering it up by desktop's USB port.
7. The runtime would be few minutes.
Thanks