LM317LILPR datasheet(7/29 Pages) TI1

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LM317L

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SLCS144E – JULY 2004 – REVISED OCTOBER 2014

8.3 Feature Description

8.3.1 NPN Darlington Output Drive

NPN Darlington output topology provides naturally low output impedance and an output capacitor is optional. To

support maximum current and lowest temperature, 2.5-V headroom is recommended (VI – VO).

8.3.2 Overload Block

Over-current and over-temperature shutdown protects the device against overload or damage from operating in

excessive heat.

8.3.3 Programmable Feedback

Op amp with 1.25-V offset input at the ADJUST pin provides easy output voltage or current (not both)

programming. For current regulation applications, a single resistor whose resistance value is 1.25 V / IOUT and

power rating is greater than (1.25 V)2 / R should be used. For voltage regulation applications, two resistors set

the output voltage. See Typical Application for a schematic and the resistor formula.

8.4 Device Functional Modes

8.4.1 Normal operation

The device OUTPUT pin will source current necessary to make OUTPUT pin 1.25 V greater than ADJUST

terminal to provide output regulation.

8.4.2 Operation With Low Input Voltage

The device requires up to 2.5-V headroom (VI – VO) to operate in regulation. With less headroom, the device

may drop out and OUTPUT voltage will be INPUT voltage minus drop out voltage.

8.4.3 Operation at Light Loads

The device passes its bias current to the OUTPUT pin. The load or feedback must consume this minimum

current for regulation or the output may be too high.

8.4.4 Operation In Self Protection

When an overload occurs the device will shut down Darlington NPN output stage or reduce the output current to

prevent device damage. The device will automatically reset from the overload. The output may be reduced or

alternate between on and off until the overload is removed.

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