Analysis of LDO Load Regulation

Load regulation refers to the change in output voltage when the load current is adjusted from a minimum value to a maximum value while the input voltage remains unchanged, that is, the ability to maintain a stable output voltage when the load current changes steadily. It is a steady-state indicator. The output load regulation indicator is usually expressed in mV in the LDO specification. From the definition, it can be seen that the smaller the load regulation, the better. When the load current changes suddenly, the smaller the output voltage change caused, the better the LDO performance.

For LDO power supply, its output voltage is different under different load current conditions. For example, assuming that the load current of a certain LDO changes from 10mA to 300mA, the output voltage changes from 3.3V to 3.28V, that is, when the load current is 10mA, the output voltage is 3.3V; when the load current is 300mA, the output voltage is 3.28V. If the load regulation is expressed in mV, it is 3.3V-3.28V=0.02V=20mV. This means that when the load current is within 10mA~300mA, the maximum output voltage change does not exceed 20mV.

Output capacitors of different sizes have different load regulation rates. The larger the output capacitor, the more stable the output voltage will be.

In the figure below, when the green Iout suddenly rises, the LDO output has an undershoot, which is the load regulation rate.

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