Power Transistor IC LM317LZ Low Current Adjustable Voltage Regulator

Power Transistor IC LM317LZ Low Current Adjustable Voltage Regulator

   ■ OUTPUT VOLTAGE RANGE: 1.2 TO 37V

   ■ OUTPUT CURRENT IN EXCESS OF 100 mA

   ■ LINE REGULATION TYP. 0.01%

   ■ LOAD REGULATION TYP. 0.1%

   ■ THERMAL OVERLOAD PROTECTION

   ■ SHORT CIRCUIT PROTECTION

   ■ OUTPUT TRANSISTOR SAFE AREA COMPENSATION

   ■ FLOATING OPERATION FOR HIGH VOLTAGE APPLICATIONS

DESCRIPTION

The LM217L/LM317L are monolithic integrated circuit in SO-8 and TO-92 packages intended for use as positive adjustable voltage regulators. They are designed to supply until 100 mA 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

SCHEMATIC DIAGRAM

ABSOLUTE MAXIMUM RATINGS

APPLICATION INFORMATION

The LM317L 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 LM317L 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 optimize 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.