CYStech Electronics Corp.

Spec. No. : C148A3

Issued Date : 2014.03.21

Revised Date :

Page No. : 7/12

LM317LA3

CYStek Product Specification

Load Regulation

The LM317L is capable of providing extremely good load regulation, but a few precautions are needed to

as close to the regulator as possible to minimize line drops which effectively appear in series with the

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.

prevents ripple from being amplified as the output voltage is increased. A 10μF capacitor should improve

ripple rejection about 15 dB at 120 Hz in a 10V application.

Although the LM317L 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.

Fig 6 shows the LM317L with the recommended protection diodes for output voltages in excess of 25V or

IC during an input short circuit.

Fig 6. Voltage Regulator with Protection Diodes