I have just made an adjustable voltage-regulator with a LM317, but i am still abit confused about the calculations...
This is the official formula provided by the manufacturers:
Vout = 1,25*(1+(R2/R1)) + Iadj*R2
However, since I must have missed the classes where breaking out variables was explained - i am real stuck.
Vague sources has led me to the following tho:
R2 = R1*((Vout/1,25)-1)
* Note that Iadj*R2 from the original formula is missing here
and
R1 = (R2*1,25)/(Vout-((50*10^-6)*R2))
* Iadj*R2 included
Trying these formulas in excel shows that the formulas for Vout and R1 renders matching results, whereas R2 differs by the amount that Iadj*R2 would give.. However, i am mathematically incapable of inserting that into the formula =(
I know that the TI-datasheet says "Because IAdj typically is 50 mA, it is negligible in most applications." However i find that ignoring it entirely (which all online calculators does), is pretty rough... Because lets say i use a 10k potentiometer for R2. That will result in: (50*10^-6)*10000 equals 0,5v. Which can be alot to some electronics...
Plus, i want all the formulas to match up =)
This is the official formula provided by the manufacturers:
Vout = 1,25*(1+(R2/R1)) + Iadj*R2
However, since I must have missed the classes where breaking out variables was explained - i am real stuck.
Vague sources has led me to the following tho:
R2 = R1*((Vout/1,25)-1)
* Note that Iadj*R2 from the original formula is missing here
and
R1 = (R2*1,25)/(Vout-((50*10^-6)*R2))
* Iadj*R2 included
Trying these formulas in excel shows that the formulas for Vout and R1 renders matching results, whereas R2 differs by the amount that Iadj*R2 would give.. However, i am mathematically incapable of inserting that into the formula =(
I know that the TI-datasheet says "Because IAdj typically is 50 mA, it is negligible in most applications." However i find that ignoring it entirely (which all online calculators does), is pretty rough... Because lets say i use a 10k potentiometer for R2. That will result in: (50*10^-6)*10000 equals 0,5v. Which can be alot to some electronics...
Plus, i want all the formulas to match up =)