LM317M datasheet(7/14 Pages) TI

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APPLICATION INFORMATION

LM317M

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 possiblility 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)

LM317M

3-TERMINAL ADJUSTABLE REGULATOR

SLVS297O – APRIL 2000 – REVISED JULY 2006

Figure 14. Adjustable Voltage Regulator

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