APPLICATION

INFORMATION

PROGRAMMING THE OUTPUT VOLTAGE

The LR8421 internal 1.2V referenc e voltage is compared to the voltage at the FB pin to generate an error

signal at the output of the error amplifier. The output voltage is set by an external resistive voltage divider

converter efficiency. The maximum value of the resistor network is limited by the feedback input bias

current and the potential for noise being coupled into the feedback pin. A resistor network less than 100k

is recommended.

Typically, a minimum current of 50 A flowing through the feedback divider gives good accuracy and noise

covering. A standard low side resistor of 24k

is typically selected. The resistors are then calculated as:

The use of 1% accuracy metal film resistor is recommended for the better output voltage accuracy.

LESHAN RADIO COMPANY, LTD.

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