Find Resistors for an LM317

Choose Two Resistors and Find the Output Voltage

Referring to Application Note 181,

• V_out may be from 1.2V to 37V at 1.5A
• V_adj should be around 50 µA
• Calculation takes into account an error correction for V_adj of 50 µA offsetting V_out

R1 (typical range 120Ω and 240Ω)

120 130 150 160 180 200 220 240

R2

10 11 12 13 14 15 16 18 20 22 24 27 30 33 36 39 43 47 51 56 62 68 75 82 91 100 110 120 130 150 160 180 200 220 240 270 300 330 360 390 430 470 510 560 620 680 750 820 910 1000 1100 1200 1300 1500 1600 1800 2200 2400 2700 300 3300 3600 3900 4300 4700 5100 5600 6200 6800 7500 8200 9100 10000 11000 12000 13000 15000 16000 18000 20000 22000 24000 27000 30000 33000 36000 39000 43000 47000 51000 56000 62000 68000 75000 82000 91000

Output Voltage	Vout =

Choose an Output Voltage and R1, and Find R2

.

Vout
R1 (typical range 120Ω and 240Ω)	120 130 150 160 180 200 220 240

R2	R2 =

For more technical data, see: National Semiconductor, LM317 - 3-Terminal Adjustable Regulator