Voltage Regulator Application Note
Various protection circuits are built into Ricoh voltage regulators.
Inrush Current Preventing Circuit
At the start-up of a voltage regulator, an inrush current equivalent to a peak current flows until the output capacitor is charged up to the set output voltage if the voltage regulator does not have an inrush current protection circuit or soft-start circuit. When the inrush current is large, the input voltage of a voltage regulator may be unstable. If there is a large input voltage drop, the operation of another connected circuit may be affected.
Ricoh provides two kinds of Inrush Current Protection Circuits, and both have different features.
|Control Method||Start up Time|
|Inrush Current Limit Circuit||Limiting with constant current.||When COUT is small, it is possible to start up quickly compared with a constant slope circuit.|
|Constant Slope Circuit||Limiting with constant time, so-called Soft Start Function.||Start-up time is fixed in the IC and start-up time does not change by the capacitance of COUT.|
RP115x has both of the inrush current protection circuit and the constant slope circuit built in, and it switches the circuits according to the capacitance of COUT. Please refer to a datasheet for details.