Adjustable boost regulator trouble

I received an adjustable boost regulator a while back and I was never able to get the output adjusted. I followed the instructions on the site and applied a 1k ohm load but the output was consistently equal to the input (and yes, I am sure I was testing the output). I’m pretty sure it is dead now because as soon as apply a power source, the batteries, wires, and board begin to heat up. I am willing to purchase another board but I fear this may happen again. Can anyone tell me what I may have done wrong or if it is possible to revive this board?


Hello Brian,

How did you connect the 1k Ohm load to the boost regulator? Also, what voltage did you apply to VIN when your boost regulator started to heat up? Do you have a good idea about how much current you were drawing from the regulator when it began to heat up? What did you have connected to VOUT when it heated up? Sometimes voltage regulators get very hot when they are working hard but this does not necessarily mean they are broken, what makes you think that it is broken now?

- Ryan

I was running 3-4v (3AAA) through it. I’m trying to remember how I had the resistor connected, as I don’t have it in front of me. I’m pretty sure I had it inline with the output. As for it heating up, it would heat up with or without something connected to the output.

Can someone show me a diagram of how it is supposed to be wired for adjusting the output voltage?

The 1k Ohm resistor should be connected between VOUT and GND of the boost regulator.

It is not typical for regulators to get hot when they are unloaded. What you describe sounds liked a short between VIN and GND. Can you post some pictures of your setup? Do you have any reason to believe that your boost regulator was exposed to a high transient voltage spike? A voltage spike on VIN could have broken the regulator chip and led to the symptoms you are now facing. For a nice primer on voltage spikes, take a look at our application note, Understanding Destructive LC Voltage Spikes.

- Ryan

I’ll have to take a picture tonight. However, I was able to go back and look at what I had done. I had a small 3AAA battery pack for a power source, 4 x 230ohm resistors in series (I didn’t have a 1k at the time), and was using a multimeter for checking output voltage. I had the resistors running in series from the output pin to the ground. After turning the potentiometer every which way with out result, I spun it round and round in both directions out of frustration. It was after that point that I noticed the heat coming from the wires, the batteries, and the board. Currently, it heats up with or without anything connected to the output pins.

Bottom line… I think I was a little over zealous and fried the regulator chip as you stated.

I’m still on the fence as to whether or not I will buy another one, not really because of the board but more because of the current that the micro-hp motors may need. Do you think this regulator can power 4 of these motors ( I plan on running two pairs in series.

Thanks again for your responses. I was beginning to feel unloved.

- Brian

If you power the boost regulator with a voltage higher than the output voltage, you can break the voltage regulator chip. At certain pot ranges, the output voltage is set to 2.5 V which is lower than the nominal voltage of the 3 AAA cells you were using. You should use an input voltage of 2.5 V or lower when adjusting your boost regulator.

What are you trying to accomplish with two pairs of motors in series? If you are trying to accomplish four wheel drive (4WD), you are not going to get good results because that circuit configuration makes a particular motor receive less and less power as it encounters more and more shaft resistance. If you can’t power each motor separately, the next best option is usually to power two pairs in parallel.

The input current to the boost regulator can be at most 2 A and the regulator is only about 80% efficient. This means the maximum output current, with no boost, is 1.6 A. Even with no boost, you are right at the limit of what the boost regulator can handle, so it doesn’t make much sense to power these motors with this boost regulator. We’ve had requests for a higher-power boost regulators; they are (deep) in our product development queue.

- Ryan

It sounds like that is exactly what I did. Oh well, lesson learned. It sounds like it probably wouldn’t have met my needs anyways.

I’m attempting to build a small 4wd rover. So far, I have the motors, sensors, and microcontroller squared away. I just need to figure out how to power it all. I’m probably just going to slap a few AA or AAA NiMH on it and call it a day.

Thanks again for your assistance.

- Brian

Hi… I’m new at robot, I have build a robot and I’m using 6V motor DC (600mA, Peak 1.4A). To reduce some batteries, I try to use adjustable boost regulator from pololu… Input voltage = 8V, output voltage = 9V. I have run my robot about 10 minutes and the regulator is heating (HOT). is it OK? or maybe any of you have other solution (other powerful boost regulator)?


Just Smile and Laugh


With the kind of load you’re putting on it, it’s definitely normal for the regulator to get hot. And if it’s running for ten minutes, you’re probably okay. We have had requests for higher-current units, so such a product is on our list of future products, but there is nothing specific in development right now.

- Jan