Searching for an ultra-low-power 12V to 3V buck converter module

[dakhnod]

Hello,

For a personal, open-source project I need to regulate 12V down to 3V, while consuming as little power as possible (a few uA quiescent current at most) in order to control a motor via BLE, all on batteries.

While I was able to find ICs like the STBLW35, I am unable to find ready-to-use small boards/modules with those ICs.

To me, it seems like the field of ultra-low-power is quite novel for the open-source space. As such, I wanted to ask whether ST could

• Share insights about suitable modules with me
• Support me and my project with products/evaluation boards

Thank you for your time,

Kind regards,

Daniel Dakhno

[Andrew Neil]

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@dakhnod wrote:

a personal, open-source project

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Could you give some more details of this project?

"ultra low power" and "motor" is an intriguing combination ...

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@dakhnod wrote:

• Support me and my project with products/evaluation boards

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For that, you're probably best to contact your local sales office or distributor - see:

https://www.st.com/content/st_com/en/contact-us.html 

[TDK]

Look on Digikey for buck converters. I am sure you can find 100 or so that fit the 12 V -> 3 V requirement. Expect efficiency in the 80% range and way more than a few uA of quescient current. You will need to know how much maximum current it needs to produce.

[dakhnod]

Hello, 

thanks for the reply!

Indeed, a motor and low-power is not so intuitive.

I have, a few years ago, created a BLE-enabled door lock, comparable to the Nuki ones. You can see it in action here: https://www.youtube.com/watch?v=jnUlXBZHBno

Now I want to develop this further, by creating a generalized 12V stepper motor controller board.

Due to BLE, I have the requirement of low power, so that the board can stay online for prolonged periods on batteries.

The motor action happens rarely, so that is not too relevant, and draws current directly from the batteries anyways.

I require 15mA peak current, at most.

Kind regards,

Daniel

[Peter BENSCH]

Is the question still open?

In order to make your design as energy-efficient as possible, it will probably have to be separated stages: the 12V can, for example, be regulated to the lowest possible voltage for the BLE module, with the motor driver remaining completely switched off (e.g. with p-ch MOSFET). Only when the motor is to be controlled would the motor driver be switched on.

The problem here, however, is the conversion from 12V to, for example, 3V with such low quiescent current requirements, because, to my knowledge, there is currently no regulator that can do this with less than a few microamperes, as @TDK already mentioned.

Since the BLE part seems to be quite energy-efficient, you could consider tapping the next higher voltage level than 3V from the batteries connected in series. Then an LDO such as the STLQ020 would probably suffice to generate the 3V for the BLE module. Unfortunately, there is currently no dedicated evaluation board that only contains the STLQ020, but it should still be possible to solder it by hand in the SOT323-5L.

Hope that still helps?

Regards
/Peter