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LM5034: VIN Input Transient

Koshi Ninomiya
Expert 4105 points
Part Number: LM5034
Other Parts Discussed in Thread: LM5134

Hi Team,

My customer is evaluating LM5034, and has a question about VIN pin application. The LM5034 datasheet shows applications information for VIN at page 19. There is the "Figure 26. Input Transient Production". The circuit of the figure 26 be used to suppress transients which may occur at the input supply. They understood that. But, they have a question if the LM51034 has any limitation of slew rate to the VIN input voltage. Because there were some power supply control ICs that could malfunction at high-speed dv / dt with an IC Vin of 20V / ms or more, so they were wondering if VIN application of LM5034 was the same intention.
Thank you.

Best Regards,

Koshi Ninomiya

  • 0
    TI__Expert 6080 points

    Hello,

    The RC circuit at the VIN pin works in a way that: when the power stage is turned-ON the input current increases proportional to the input voltage. When the UVLO threshold is reached the outputs are enabled and the external VCC supply gets activated and provides for the IC power. At this stage, the "RC" circuit enables the current into the VIN pin to drop to a 120uA typ value. This prevents any transients on the input rail. That seems to be the only reason why this circuit exists there. 

    Also, I am not sure what you mean by LM51034, I assume you meant LM5134; in that case, that controller is a gate driver and LM5034 is a current mode PWM controller they are incomparable.

    Regards,

    Sonal

  • 0 in reply to Sonal Singh
    TI__Expert 4105 points

    Hi Sonal-san,

    Thank you for your reply. I understood that the LM5034 did not have any limitation of slew rate to the VIN input voltage.
    I was sorry that "LM51034" was typo.

    Best Regards,

    Koshi Ninomiya