General​​ Description​​ ​​ 

The EM317L​​ is an adjustable 3-terminal positive voltage regulator​​ capable of supplying​​ 100mA​​ over an output voltage range of 1.2 V to 37 V. This voltage regulator is exceptionally easy to use and requires only two external resistors to set the output voltage. Further, it employs internal current limiting,​​ thermal shutdown and safe area compensation, making it essentially blow​​ out proof.​​ 


EM317L​​ offers full overload protection. Included on the chip current limit, thermal overload protection, and safe-area protection. Normally, no capacitors is 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 added to improve transient response.​​ 



  • Output current up to 100mA

  • Output Voltages 1.2V to 37V

  • Internal thermal overload protection

  • Internal short​​ circuit​​ current limiting

  • Output transistor safe area compensations

  • Available in TO-92, SOP8 and SOT89 packages



  • Voltage Regulators

  • Power Supplies

  • Current Regulators

  • Switching Regulators

  • Current Limiter

  • Constant Current Battery Charger

  • Current Limited Charger


Typical Application Circuit










*​​ CIN is required if regulator is located an appreciable distance from power supply filter

**​​ CO is not needed for stability, however, it improve transient response.


Since IADJ​​ is controlled to less than 100µA, the error associated with this term is negligible​​ in most applications.



Marking Information and Pin Configurations (Top View)















Ordering Information






















Green products:​​ ​​ 

  • Lead-free (RoHS compliant)​​ ​​ 

  • Halogen free(Br or Cl does not exceed 900ppm by weight in homogeneous material and total of Br and Cl does not exceed 1500ppm by weight


Absolute Maximum Ratings









Recommended Operating Conditions​​ 







Block Diagram



























Electrical Characteristics​​ (Unless otherwise noted, VI​​ - VO​​ = 5V and IO= 40mA. TJ​​ = 0°C to 125°C, unless otherwise noted)



























Note 1: All characteristics are measured with a 0.1µF capacitor across the input and a 1µF capacitor across the output.​​ 

Note 2: Input regulation is expressed here as the percentage change in output voltage per 1V change at the input.​​ 

Note 3: Since long-term drift cannot be measured on the individual devices prior to shipment, this specification is not​​ 

intended to be a guarantee or warranty. It is an engineering estimate of the average drift to be expected from lot​​ 

to lot.













Application Information


  • Basic Circuit Operation

The​​ EM317L is a 3- terminal floating regulator. In operation, tit develops and maintains a nominal 1.25V reference (VREF) between its output and adjustment terminal. This reference voltage is converted to a programming current flow through R2 to ground.


The regulated output voltage is given by:



















Since the current from the adjustment terminal (IADJ) represents an error term in the equation, the​​ EM317Lwas designed to minimize IADJ​​ and make it very constant with line and load changes. To do this, all quiescent operating current is returned to the output establishing a minimum load current requirement. If there is insufficient load on the output, the output will rise.


Since the​​ EM317L is a floating regulator, it is only the voltage differential across the circuit which is important to performance, and operation at high voltages with respect to ground is possible.


  • Load Regulation

The​​ EM317L is capable of providing extremely good load regulation, but a few precautions are needed to obtain maximum performance. For best performance, the programming resistor R1 should be connected as close to the regulator as possible to minimize line drops which effectively appear in series with the reference, thereby degrading regulation. The ground end of R2 can be returned near the load ground to provide remote ground sensing and improve load regulation.


  • External Capacitors

A 0.1µF disc or 1.0µF tantalum input bypass capacitor CIN​​ is recommended to reduce the sensitivity to input line impedance. The adjustment terminal may be bypassed to ground to improve ripple rejection. This capacitor CADJ​​ prevents ripple from being amplified as the output voltage is increased. A 10µF capacitor should improve ripple rejection about 15 dB at 120Hz in a 10V application.


Although the​​ EM317L is stable with no output capacitance, like any feedback circuit, certain values of external capacitance can cause excessive ringing. An output capacitance CO​​ in the form of a 1.0µF tantalum or 25µF aluminum electrolytic capacitor on the output swamps this effect and insures stability.



  • Protection Diodes

When external capacitors are used with any IC regulator, it is sometimes necessary to add protection diodes to prevent the capacitors from discharging through low current points into the regulator.


The figure below shows the​​ EM317L with the recommended protection diodes for output for output voltage in excess of 25V or high capacitance values (CO​​ > 25µF, CADJ​​ > 10µF). Diode D1 prevents CO from discharging thru the IC during an input short circuit. Diode D2 protects against capacitor CADJ​​ discharging through the IC during an output short circuit. The combination of diodes D1 and D2 prevents CADJ​​ from discharging through the IC during an input short circuit.






















Package Outline Dimensions – TO 92























Package Outline Dimensions​​ ​​ SOP​​ 8





















Package Outline Dimensions – SOT 89