SLCS144G July   2004  – August 2026 LM317L

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information (SOIC & SOT-89)
    5. 5.5 Thermal Information (TO-92 & TSSOP)
    6. 5.6 Electrical Characteristics
    7. 5.7 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 NPN Darlington Output Drive
      2. 6.3.2 Overload Block
      3. 6.3.3 Programmable Feedback
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal operation
      2. 6.4.2 Operation With Low Input Voltage
      3. 6.4.3 Operation at Light Loads
      4. 6.4.4 Operation In Self Protection
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Input Capacitor
        2. 7.2.2.2 Output Capacitor
        3. 7.2.2.3 Feedback Resistors
        4. 7.2.2.4 Adjustment Terminal Capacitor
        5. 7.2.2.5 Design Options and Parameters
        6. 7.2.2.6 Output Voltage
        7. 7.2.2.7 Input Short Protection
        8. 7.2.2.8 Ripple Rejection
      3. 7.2.3 Application Curve
    3. 7.3 System Examples
      1. 7.3.1 Regulator Circuit With Improved Ripple Rejection
      2. 7.3.2 0V to 30V Regulator Circuit
      3. 7.3.3 Precision Current-Limiter Circuit
      4. 7.3.4 Tracking Preregulator Circuit
      5. 7.3.5 Slow-Turn On 15V Regulator Circuit
      6. 7.3.6 50mA Constant-Current, Battery-Charger Circuit
      7. 7.3.7 Current-Limited 6V Charger
      8. 7.3.8 High-Current Adjustable Regulator
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
    6. 7.6 Estimating Junction Temperature
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Device Nomenclature
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.1 Overview

The LM317L is a 100mA linear regulator with high voltage tolerance up to 37V (CSO: TID & CSO: RFB). The device has a feedback voltage that is relative to the output instead of ground. This ungrounded design allows the LM317L to have superior line and load regulation. This design also allows the device to be used as a current source or current sink using a single resistor. Any output voltage within the recommended output range can be obtained by using two resistors. The bias current of the device flows to the output; this current must be used by the load or the feedback resistors. Refer to the minimum output current to maintain regulation in the Electrical Characteristics.

The power dissipation is the product of pass transistor voltage and current, which is calculated as shown in Equation 1.

Equation 1. PD = (VIN – VOUT) × IOUT

The application heat sink must be able to absorb the power calculated in Equation 1.

The LM317L regulator offers current-limiting and thermal-overload protection. All overload-protection circuitry remains fully functional even when ADJUSTMENT is disconnected. Normally, no capacitors are needed unless the device is situated far from the input filter capacitors, in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. ADJUSTMENT can be bypassed to achieve very high ripple rejection, which is difficult to achieve with standard three-terminal regulators.

In addition to replacing fixed regulators, the LM317L regulator is useful in a wide variety of other applications. Because the regulator is floating and observes only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input-to-output differential is not exceeded. The primary application is that of a programmable output regulator, but by connecting a fixed resistor between ADJUSTMENT and OUTPUT, this device can be used as a precision current regulator. Supplies with electronic shutdown can be achieved by clamping ADJUSTMENT to ground, programming the output to 1.25V, where most loads draw little current.