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TIDA-01505: start-up circuit calcul of the total resistance for the fast start-up

Hassan KHALIL
Prodigy 90 points
Part Number: TIDA-01505

Hello,

in the datasheet of TIDA-01505, it's indicated that the minimimum required start-up current is 103mA. With current of 103mA and Vin_min 50V, we obtain a resistor of 313ohms but in your, you use six resistors of 50ohms, what is the reason if the required resistor is 313ohms? then the maximum start-up current is 3.3mA and not 103mA

  • 0
    TI__Mastermind 18120 points

    Hi Hassan,

    The formula calculates the required resistance value in order to achieve 1.8ms start up speed ideally. However it is a compromise with the power dissipation in the resistors. high ohmic resistors are selected to ensure the power dissipation is lower than 0.55W at 1kV input. You may reduce the overall resistance in the fast lane to increase the startup speed but there is a thermal limitation on top.