TPS61022: Low voltage input with VIN bias

Hi Steven,

What's your output voltage? TPS61021A supports minimum 0.9V startup, which fits for your application.

Hi, I would love 6V but would settle with 5V. Looking to get as much current out of the battery as possible over a very short time.

Hi Steven,

Forget to ask you the output current? AA alkaline battery has quite larger internal resistance high to ~hundreds of mohm. If too much current is drawn, the battery voltage will be drawn to very low.

Hi, as much as possible! This is for a competition entry which needs to power a motor as fast as possible from a single AA for less than 10 seconds.

The state of the battery afterwards isn't important. Will start with a fresh battery.

Hi Steven,

I understand you want as much as possible. But at least tell me the maximum Iout that I want. The reason is TPS61022 is a internal compensated device which means it's stable in particular Vin, Vout, Iout range. If your circuit working condition is unique, I'm worried the device may be loop unstable.

Another device TPS61089 may fits for your demand. Here is a reference design: TIDA050039. TPS61089 Vin pin is powered by externally. 

Hi, I was hoping for 0.5A on the 5V side.

Thanks

Hi Steven,

So the output power is 5V*0.5A=2.5W, when AA alkaline battery is 1.5V, TPS61022 average input current is 2A. Does AA alkaline has the capability to output 2A? Maybe you can use two alkaline in series to reduce the current.

If you insist using one AA alkaline, you can follow below schematic. Please add a 22pF feedforward capacitor ++ 1kohm resistor in parallel with R1.  

Hi, thanks. Can you just confirm that would start up with the 1.5V input as it shows VIN and the inductor connected together? Or did you mean if I power vin externally and connect the inductor to the AA?

Thanks

I need to try it on bench tomorrow. Will let you know the result.

Hi Steven,

Sorry TPS61022 Vin cannot be supplied externally.