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LM3409HV: What is the frequency of the gate pin?

Louis Panzarella
Prodigy 20 points
Part Number: LM3409HV
Other Parts Discussed in Thread: LM3409

The TI LM3409HV P-FET Buck Controlled (HVSSOP version) is currently used in one of the systems in my company.  I am trying to understand the switching frequency of pin-6 (PGATE).  This pin is connected to the gate of  P-Channel MOSFET in the system's Buck circuit.  Once I know the PGATE (pin-6) frequency I will be able to calculate the output voltage of the Buck circuit.  Can someone tell me how to calculate the PGATE (pin-6) frequency?

  • 0
    TI__Mastermind 28655 points
    Hello Louis,

    P-gate frequency will not tell you the output voltage. The LM3409HV is a constant off-time hysteretic controller for regulating current, not voltage. The off-time is based on the output voltage, Roff and Coff. The switching frequency (also the gate frequency) is determined by Vin, Vout (the voltage across the load when the LM3409 is regulating current), Roff and Coff. This buck converter is a current regulator so the output voltage depends on the load. If there is no load or very light load the output voltage will be the input voltage.

    When running continuous current as a current regulator the output voltage can be figured out by the duty cycle and input voltage. Notice the LM3409 does not regulate output voltage it regulates current. The datasheet has the design equations to allow design of a current regulator, it may be a good start to go through those.

    Best Regards,
  • 0 in reply to Irwin Nederbragt
    TI__Mastermind 28655 points
    I have not heard back from you so I believe you may have solved the issue.
    The thread will close now but will reopen if you reply.

    Best Regards,