LM317SSLASHNOPB datasheet(27/51 Pages) TI

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LM317-N

LM117, LM317-N

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SNVS774Q – MAY 2004 – REVISED JUNE 2020

Product Folder Links: LM117 LM317-N

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Typical Applications (continued)

9.2.16 Current-Limited 6-V Charger

The current in a battery charger application is limited by switching between constant current and constant voltage

states (see Figure 34). When the battery pulls low current, the drop across the 1

Ω resistor is not substantial and

the NPN remains off. A constant voltage is seen across the battery, as regulated by the resistor divider. When

current through the battery rises past peak current, the 1

Ω provides enough voltage to turn the transistor on,

pulling ADJ close to ground. This results in limiting the maximum current to the battery.

*Sets peak current (0.6A for 1Ω)

**The 1000-μF is recommended to filter out input transients

Figure 34. Current-Limited 6-V Charger

9.2.17 Digitally Selected Outputs

Figure 35 demonstrates a digitally selectable output voltage. In its default state, all transistors are off and the

output voltage is set based on R1 and R2. By driving certain transistors, the associated resistor is connected in

parallel to R2, modifying the output voltage of the regulator.

*Sets maximum VOUT

Figure 35. Digitally Selected Outputs

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LM317S/NOPB Datasheet(PDF) 27 Page - Texas Instruments