LM317D2T

DESCRIPTION

The LM317D2T are monolithic integrated circuit in TO-3and 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.

Features

    1. OUTPUT VOLTAGE RANGE : 1.2 TO 37V

    2. OUTPUT CURRENT IN EXCESS OF 1.5A

    3. 0.1% LINE AND LOAD REGULATION

    4. FLOATING OPERATION FOR HIGH VOLTAGES

    5. COMPLETE SERIES OF PROTECTIONS :

          - CURRENT LIMITING, THERMAL SHUTDOWN AND SOA CONTROL

APPLICATION INFORMATION

The LM117/217/317 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 , giving an output voltage VO of:

                  Basic Adjustable Regulator

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 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