Pololu step-up converter drops voltage

Question

I have a Pololu 3.3V step-up converter - U1V11F3. I tested it by connecting a regular 1.5V alkaline battery for input and a resistor at output. With no load or small load (10K) it keeps the output voltage at 3.3, however with higher loads (100 ohm) it drops the voltage to 3.13 with a current of 31 mA and with 47 ohm and current of about 60 mA it drops to 2.7-2.8

I have noticed that the current for the battery goes as high as 150 mA during that time and the measured voltage drops from 1.46 to 1.24

Does this mean that the battery is not able to provide a high enough current? Looking at the datasheet for the converter chip it should keep the voltage up to 300 mA output current. My intended use for the converter is an Arduino compatible node with RFM69HW chip that should sleep most of the time, but wake up and send radio data which should increase the current to about 130 mA for short periods of time, but obviously the converter can't keep up with the demand. I can try not to use the highest power of the chip, but still the current will be in the tens of mA which apparently will not work.

Does anybody know if other chips are working better? Or has anyone experience with a similar working configuration?

Answer 1

The datasheet does say 300 mA, but only when Vin > 2.4V. Take a look at the efficiency vs. output current curves for Vo = 3.3V. You will see different curves for Vin = 2.4V, 1.8V, and 0.9V. Note that the 1.8V efficiency curve stops at 130 mA (at 78%). In other words, if you have only 1.5V, forget about outputting 130 mA. You need more input voltage or a beefier converter.

I'm not sure why your battery had 150 mA going through it, but it sounds like your boost converter didn't have the capacity to operate at the load you were driving it at. And why are you trying loads as low as 47 ohms? Most circuits are designed with high Rin so as not to load the previous stage. I suggest figuring out the Rin of the circuit you are connecting this boost converter to and inserting a buffer if it's too low.

I recommend watching this EEVblog video where Dave goes through the process of selecting a DC-DC boost converter. Dave goes through what factors you need to consider when selecting a boost converter and how you should read a converter datasheet.