LM317 Calculator

LM317 Calculator or LM317 Toolkit Software

Program to calculate the resistance at a LM317 / LM117. Because you can get correct regulated output voltage using this LM317 calculator.

The LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37 V. Also It requires only two external resistors to set the output voltage. The device features a typical line regulation of 0.01% and typical load regulation of 0.1%. It includes current limiting, thermal overload protection, and safe operating area protection. Overload protection remains functional even if the ADJUST terminal is disconnect.

LM317 calculation

The LM317 provides an internal reference voltage of 1.25 V between the output and adjustments
terminals. This voltage use to set a constant current flow across an external resistor divider giving an output voltage VO of:
VO = VREF (1 + R2/R1) + IADJ R2
This ic design to minimize the term IADJ (100 µA max) and to maintain it very constant with line and load changes. Usually, the error term IADJ × R2 can be neglect. To obtain the previous requirement, all the regulator quiescent current is returned to the output terminal, imposing a minimum load current condition. If the load is insufficient, the output voltage will rise. Since the LM317 is a floating regulator and “sees” only the input-to- output differential voltage, supplies of very high voltage with respect to ground can be regulated as long as the maximum input-to-output differential is not exceeded.

Also Check This post – LM317 power supply circuit schematic

LM317 Regulator design

Furthermore, programmable regulators are easily obtainable and, by connecting a fixed resistor between the adjustment and output, this device can use as a precision current regulator. In order to optimize the load regulation, the current set resistor R1 should be install as close as possible to the regulator, while the ground terminal of R2 should be near the ground of the load to provide remote ground sensing. Performance can improve with added capacitance as follow:

• An input bypass capacitor of 0.1 µF
• An adjustment terminal to ground 10 µF capacitor to improve the ripple rejection of about 15 dB (CADJ).
• An 1 µF tantalum (or 25 µF Aluminium electrolytic) capacitor on the output to improve transient response In addition to external capacitors, also good practice to add protection diodes,

LM317 toolkit software is completely free but fully functional and easy to use. Finally it runs under Microsoft Windows NT, 2000, XP, Vista and Seven .

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Source:https://www.ulrichradig.de

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