SNVSAC2A March 2015 – June 2020 LM317A
PRODUCTION DATA.
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.
NOTE:
*Sets peak current (0.6A for 1Ω)