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LM63635-Q1: output rate and pwm duty cycle

Victor Levy
Intellectual 2436 points
Part Number: LM63635-Q1

Hello,

my customer has the following question, 

"

Please find question related to PSU condition

Input voltage : 10v to 24v

(Output voltage : 9v @ 2A (heater resistor 

If the input will drop to rates below 10v (but no lower than 6v) , what will be

  • Output rate?
  • PWM Duty cycle?

"

Thank you.

  • 0
    TI__Mastermind 23845 points

    HI Victor,

    If the input drops below 10V and start to approaching 9V, PWM duty cycle will be maximum meaning that you will be limited only by minimum off time of the converter.

    You can see similar behavior on the 5V output case as shown on the figure 14

    http://www.ti.com/lit/ds/symlink/lm63635-q1.pdf#page=21

    During dropout, the Vout will follow the Vin, the converter will still be switching and providing the power to the output. The only difference is that now the output voltage is no longer 9V but instead will be lower than Vin and it is due to the losses from internal High Side MOSFET, Inductor series resistance, etc

    The output drop rate will follow the input drop rate

    Thanks

    -Arief