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Why does the output voltage of 3-terminal regulator drops?

Latest Updated:12/01/2011

Question:

The output voltage of the 3-terminal regulator drops when a load is connected.

Answer:

The possible causes and actions are as follows.

Cause: The output oscillates.
Action: Check connection of the capacitor connected between input and output.

Cause: A current exceeding the peak output current flows.
Action: Lower the input voltage. Effectively dissipate the heat to lower the chip temperature.
Caution A high current is required for starting the regulator when a motor or a lamp is connected as the load.

Cause: The chip temperature exceeds 150°C.
Action: Lower the input voltage. Effectively dissipate the heat to lower the chip temperature.

Cause: The input and output are connected in reverse.
Action: Check the pin connection.

Cause: The capacitance of the previous-step power supply is insufficient (in the case of a low-saturation regulator).
Action: When a low-saturation regulator is used, prepare a power supply that can supply a circuit operating current at startup, as well as an output current.
Suitable Products
3 Terminal Regulators