# Voltage Regulator and Resistors for LED Circuit

I'm trying to design a circuit to power 17 LEDs. The LEDs I'm using are AA2810AQBS/D Blue SMD LEDs with 3.3v Forward Voltage at 20mA.

I would like to power this using EITHER 2xAA Alkaline batteries OR a 5V USB battery pack.

I was looking at the AAT1217-3.3, 3.3V Step Up Converter but I'm not sure if 3.3V is enough and it's unclear to me if this can accept the voltage range that I need for 2xAA's or 5V battery pack (potential battery voltage range of 2.4V to 6V?)

Can I power these LEDs with 3.3V and 1 ohm current limiting resistors?

Any suggestions on a low cost regulator and LED current limiting resistors for my needs?

• Your looking for a current source not a voltage source.. Commented Oct 6, 2017 at 16:55
• What is time duration, tolerance on If, min efficiency and cost budget, SMT board design etc.? You question is insufficient. Commented Oct 6, 2017 at 17:02
• @TonyStewart.EEsince'75 Thanks for the help. I would like the 2xAA batteries to last all day... so 8+ hours is ideal. The board will be a flexible PCB with SMDs. I might make a lot of these, so would like the costs to be as low as possible (like under $1-$2 for regulator hardware). Otherwise, I don't have any other requirements. Tolerance on If is whatever these LEDs could handle without flickering. Commented Oct 6, 2017 at 18:09
• MAybe you need something like or a few of these st.com/content/ccc/resource/technical/document/datasheet/13/6a/… Commented Oct 6, 2017 at 20:09
• Commented Oct 6, 2017 at 20:12

## Lowest cost solution from a battery.

• Load Power = 3.3V*20mA*17=1.1W @340mA , which would be short operating time for AA's and 5V USB pack has no tolerance specs, cost or other obvious assumptions were given.

• until then, this is the cheapest.

simulate this circuit – Schematic created using CircuitLab

If Vf@20mA is matched with 1% ( expected from same batch) and Board has good copper heat radiation on pads for cooling, you can eliminate all the R's and drive with 3.3V Buck regulator rated for >350mA.