App note: Simple test method for estimating the stability of linear regulators


Tips from ROHM Semiconductor to estimate the stability of linear regulator using simple step response method. Link here (PDF)

Low drop-out (LDO) regulators developed back in the age when large-capacitance multi-layer ceramic capacitors (hereinafter, MLCCs) were uncommon cause a phase delay, leading to oscillation when connected to a low-ESR capacitor like an MLCC. Often, MLCCs are used to save board space and prolong the lives of electronic components. A resistor placed in series in the circuit increases apparent ESR and establishes a phase lead that enable the use of an MLCC as an output capacitor. Phase margin measurement is practical on an LDO having variable output voltage, since its feedback loop is outwardly exposed. However, on a fixed output voltage LDO, the phase margin cannot be measured because of its closed loop circuit.

App note: Linear regulators reverse voltage protection


Various input and output reverse voltage protection method for linear regulators discussed in this app note from ROHM. Link here (PDF)

A linear regulator integrated circuit (IC) is a DC-to-DC buck converter system that reduces a DC supply from higher voltage level to a lower voltage level, thus it requires that the input voltage is always higher than the regulated voltage. Output voltage, however, may become higher than the input voltage under specific situations or circuit configurations, and that reverse voltage and current may cause damage to the IC. A reverse polarity connection or certain inductor components can also cause a polarity reversal between the input and output terminals. This application note provides instructions on reversed voltage polarity protection for ICs.

App note: Power source ON/OFF characteristics for linear regulator


A good read app note from ROHM on linear regulator On and Off characteristic. Link here (PDF)

When a linear regulator IC is turned ON, the electric charge is stored in the output capacitor and the output voltage increases up to the specified value. At this time, an inrush current flows from the input to output of the IC. The output voltage drops when the input power source is disconnected. This application note explains the series of operations when the power source is turned ON/OFF.