### ELECINF344/381

Interactive web site of Télécom ParisTech's ELECINF344/ELECINF381 Robotics and Embedded Systems classes (a.k.a. ROSE, 2012 session).

# Tutobot: power supply for the motors

The motors we choose are 6V nominal but the documentation says they can be driven with 9V. The stall current is of 360mA.

I choose a driver IC we had on our mentor graphics library, the L6206. I have one uncertainty about it, it’s its over current protection. The datasheet gives information on how to calibrate the current threshold using a resistance between 5k and 40k.   The problem is that the minimum threshold previewed (with a 40k resistance) is about 552 mA, which is above the stall current. I am not sure this is a big problem, if anyone has comments I’d appreciate =].

Meanwhile I am searching a voltage regulator for the motor. It has to generate the 9V with 800mA, from the voltage coming from the battery/usb system. This input voltage is not constant and may vary from 2.5 to 4.2 V. Looking for some options at Linear technologies, I found some ICs, and narrowing down to the simpler and most adapted ones I got these:

http://www.linear.com/product/LTC1872

http://www.linear.com/product/LT1370

None are available in our library, so one of them needs to be added. I could not see important differences between them, but I think the 1872 is a little more powerful than we need. For now I am going with the 1370.

Possibly related posts:

### 2 comments to Tutobot: power supply for the motors

• LT3479 might be an other option : higher switching frequency (–> smaller inductor)

• Thalita

Their datasheet says a 4.7μH or 10μH inductor is used in most applications, and they have an circuit example boosting 5v to 12V 800mA 1MHz that uses a 4,7 µH inductor, which is the same value used in the analogous example circuits of the other two. Also accordingly to their datasheet, using a high switching frequency reduces efficiency.

But maybe what you said was about the physical size of the inductor. On this case I am not sure. The datasheet says though that a physically bigger inductor increases efficiency.

The other two seem easier to solder too…

Edit: I was just checking the prices and the 3479 is 5,25 € at digikey, the 1370 is 10.61 €. That would be a pro for the 3479.