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SHDN shutdown mode in D24V3F3 switching regulators

Hello Guys,

I have purchased the following switching regulator module:
https://eckstein-shop.de/Pololu-33V-300mA-Step-Down-Spannungsregler-D24V3F3

It would be extremely handy for me to reduce the 2mA quiescent current to 20µA using the pull-low pin since I have a battery and low power application. I would like to wake up my Arduino each 1 minute and record some sensor values. How can I realize that in combination with also pulling the voltage regulator low between the measurements?

Thank you!

Hello.

In case it is not clear, driving SHDN low turns off the output of the regulator, so if you are powering the Arduino from the regulator, it does not seem practical to turn it off. If that is not the case, you might be able to connect the SHDN signal to an Arduino pin and have the Arduino drive it low before going to sleep.

By the way, you might consider using the 600mA Step-Down Voltage Regulator D36V6F3 instead of the 3.3V, 300mA Step-Down Voltage Regulator D24V3F3. The 600 mA D36V6Fx family of step-down voltage regulators offer a lower quiescent current. (Please see the note on the 3.3V, 300mA Step-Down Voltage Regulator D24V3F3 product page for more details.)

- Amanda

Dear Amanda,
Thanks for your fast, friendly and helpful reply. The step-down converted you suggested, i.e. the D36V6F3, looks great with quiescent currents below 100µA. I will order a few of those and test them for my application. Are there modules with even lower quiescent current? I am asking just because of curiosity but <100µA is already great.

I hope I can bother you with another question. In my project, I’d like to charge 4x1.2V NiMH (low self-discharge batteries) with a fully charged voltage of 5.8 using a 12V solar panel (115x85cm in size, widely available).
I have purchased this module:


Is there maybe a module that better suits my application? Shall I use a diode between the battery pack and the step-down converter to prevent charges to flow back to the step-down converter if there’s no charging?

Thank you!
Marco

Hi, Marco.

We do not have any step-down regulators with a maximum quiescent current lower than 100µA. (If you’re interested, you can see what we have in this sortable comparison table.)

Regarding your next set of questions, we do not have much experience with battery charging circuits, but our understanding is that constant-voltage charging is generally not suitable for NiMH batteries.

- Amanda

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Thank you Amanda!
The charging current via the solar module I use should be anyways quite low with <100mA:

Using 2100mAh batteries this would result in a recharge rate of C/20. However you are right that NiMH should be charged with a constant current. I will look a bit more into this.

Thank you also for providing me with the sortable comparison table.

Marco

1 Like