How can the load transient response of an LDO be improved?

Increasing the capacitance of the output capacitor COUT is effective in improving the load transient response of an LDO.

The relationship equation between the output voltage variation (∆VOUT) and the output capacitor (COUT)

During a sudden load current change, the output voltage variation (∆VOUT) and the output capacitor (COUT) can be expressed as follows.
Therefore, increasing the capacitance of COUT reduces the output voltage variation ∆VOUT, resulting in improved load transient response.
However, increasing the capacitance could cause inrush current, and oscillation. In addition, it is important to pay attention to the VOUT startup characteristics.
For more details, please refer to the application note titled
“Load Transient Response of LDO and Methods to Improve it”

COUT : Output capacitor
∆VOUT : Output voltage variation
∆IOUT : Output current variation
T : the duration during which current flows

Note:

  • The above equation is a simplified approximation.
  • For ceramic capacitors, please consider the effective capacitance, as it may vary depending on the applied voltage.

Related Links

The following documents also contain related information.

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Product page Low-Dropout Regulators (LDO Regulators)
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