LM317 voltage and current regulator
Adjustable voltage and current-source calculations with adjust-pin current and resistor tolerance.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Setpoint: VOUT = VREF(1 + R2/R1) + IADJ R2
Assumptions
- Reference and resistor tolerances are worst-case independent corners; adjust-pin current is held at its entered value.
- Datasheet minimum load, headroom and adjust current vary with device and operating conditions. Add protection and bypass components as specified by the selected datasheet.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Circuit
- voltage
- Input voltage
- 12 V
- Reference voltage
- 1.25 V
- Adjust-pin current
- 0.00005 A
- OUT-to-ADJ resistor
- 240 Ω
- ADJ-to-ground resistor
- 720 Ω
- Each resistor tolerance
- 1 %
- Reference tolerance
- 1 %
- External voltage-mode load
- 0.05 A
- Current-source load voltage
- 3 V
- Required input-output headroom
- 3 V
- Required minimum regulator load
- 0.01 A
Results
- Regulator OUT-pin voltage
- 5.036 V
- Regulator OUT / current-source load current
- 0.0552083 A
- Output voltage / current
- 5.036 V
- Minimum tolerance setpoint
- 4.912125148514852 V
- Maximum tolerance setpoint
- 5.162875151515151 V
- R1 power
- 0.00651042 W
- R2 power
- 0.019908 W
- Regulator dissipation
- 0.384882 W