LM317KCS datasheet(7/22 Pages) TI

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APPLICATION INFORMATION

LM317

240

Ω

IAdj

Adjust

Ci (Note A)

0.1

µF

CO (Note B)

1.0

µF

VO (Note C)

NOTES: A. Ci is not required, but is recommended, particularly if the regulator is not in close proximity to the power-supply filter

capacitors. A 0.1-

µF disc or 1-µF tantalum provides sufficient bypassing for most applications, especially when adjustment

and output capacitors are used.

B. CO improves transient response, but is not needed for stability.

C. VO is calculated as shown:

Because IAdj typically is 50 µA, it is negligible in most applications.

D. CADJ is used to improve ripple rejection; it prevents amplification of the ripple as the output voltage is adjusted higher. If

CADJ is used, it is best to include protection diodes.

E. If the input is shorted to ground during a fault condition, protection diodes provide measures to prevent the possibility of

external capacitors discharging through low-impedance paths in the IC. By providing low-impedance discharge paths for

CO and CADJ, respectively, D1 and D2 prevent the capacitors from discharging into the output of the regulator.

Output

Input

Vref = 1.25 V

+ Vref 1 )

) (IAdj

D1 (Note E)

1N4002

D2 (Note E)

1N4002

CADJ (Note D)

LM317

3-TERMINAL ADJUSTABLE REGULATOR

SLVS044R – SEPTEMBER 1997 – REVISED APRIL 2007

Figure 1. Adjustable Voltage Regulator

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