What is the supply current of an LDO regulator? What are the merits and demerits of using an LDO regulator with low supply current?

Supply current refers to the input current to an LDO regulator at no load, which flows inside the IC in order to operate.

The power consumption of an LDO regulator can be calculated as

(Input Voltage) x (Consumption current of IC itself) + (Input Voltage - Output Voltage) x (Load current)

If "load current" is very small, the consumption current of IC itself cannot be ignored.

By using a low-supply-current LDO regulator for a circuit block operating at all times, the operating time of a battery-powered application can be prolonged. On the other hand, low-supply-current LDO regulators have tendency to be inferior to those with large supply current in response characteristics.

To meet various demands, we can provide LDO regulators with mode switch-over functions between low power mode and fast response fixed mode achieving both low supply current and good transient response characteristics.

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