LM317K 1.2V TO 37V VOLTAGE REGULATOR:Pinout, Datasheet, and Applications

The LM317K are monolithic integrated circuit in TO-220, ISOWATT220, TO-3 and D2 PAK packages intended for use as positive adjustable voltage regulators.

They are designed to supply more than 1.5A of load current with an output voltage adjustable over a 1.2 to 37V range.

The nominal output voltage is selected by means of only a resistive divider, making the device exceptionally easy to use and eliminating the stocking of many fixed regulators.

LM317K Symbol

LM317K Footprint

LM317K 3D Model

■ OUTPUT VOLTAGE RANGE : 1.2 TO 37V 

■ OUTPUT CURRENT IN EXCESS OF 1.5A 

■ 0.1% LINE AND LOAD REGULATION 

■ FLOATING OPERATION FOR HIGH VOLTAGES 

■ COMPLETE SERIES OF PROTECTIONS : CURRENT LIMITING, THERMAL SHUTDOWN AND SOA CONTROL

STMicroelectronics LM317K technical specifications, attributes, parameters and parts with similar specifications to STMicroelectronics LM317K.

LM317K Functional Block Diagram

It provides an internal reference voltage of 1.25V between the output and adjustments terminals. This is used to set a constant current flow across an external resistor divider (see fig. 4), giving an output voltage VO of: VO = VREF (1 + R2 R1 ) + IADJ R2 The device was designed to minimize the term IADJ (100µA max) and to maintain it very constant with line and load changes. Usually, the error term IADJ ⋅ R2 can be neglected. 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 LM117/217317 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. Furthermore, programmable regulator are easily obtainable and, by connecting a fixed resistor between the adjustment and output, the device can be used as a precision current regulator. In order to optimise the load regulation, the current set resistor R1 (see fig. 4) should be tied 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 may be improved with added capacitance as follow: An input bypass capacitor of 0.1µF An adjustment terminal to ground 10µF capacitor to improve the ripple rejection of about 15 dB (CADJ). An 1µF tantalium (or 25µFAluminium electrolitic) capacitor on the output to improve transient response. In additional to external capacitors, it is good practice to add protection diodes, as shown in fig.5. D1 protect the device against input short circuit, while D2 protect against output short circuit for capacitance discharging.

STMicroelectronics is a French-Italian multinational electronics and semiconductors manufacturer headquartered in Plan-les-Ouates near Geneva, Switzerland. The company resulted from the merger of two government-owned semiconductor companies in 1987: "Thomson Semiconducteurs" of France and "SGS Microelettronica" of Italy. It is commonly called "ST", and it is Europe's largest semiconductor chip maker based on revenue. While STMicroelectronics corporate headquarters and the headquarters for EMEA region are based in the Canton of Geneva, the holding company, STMicroelectronics N.V. is incorporated in the Netherlands.

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