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TPS7B7701-Q1: Maximum transient output current

Ansel Song
Expert 3890 points
Part Number: TPS7B7701-Q1

Hi team,

Under certain conditions, such as input 13.5V, output 5V. Is the maximum transient current the threshold for overcurrent protection?

Best regards,

Ansel

  • 0
    TI__Mastermind 23361 points

    Hi Ansel,

    The current limit needs some time to kick in, and during the startup, the in-rush current could go higher than the current limit. Here is a scope-shot that shows the internal current limit kicks in when the device is started with short-to-ground on with the 5V output with the EVM. 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Expert 3890 points

    Hi Jason,

    Therefore, the transient current will be larger than the protection current, because the current limit takes time to work.

    So can the maximum transient current be understood as the maximum current that the power device such as MOSFET, can withstand?

    Best regards,

    Ansel

  • 0 in reply to Ansel Song
    TI__Mastermind 23361 points

    Hi Ansel, 

    Having an in-rush current higher than the current limit for a short period of time is common during the startup of the device and will not cause damage to the device. But running the device continuously in the current limit may affect the long term reliability of the device. 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Expert 3890 points

    Hi Jason,

    Having an in-rush current higher than the current limit, this will happen during the start-up of device. There is also a situation that occurs during continuous operation but the load suddenly changes, resulting in an instantaneous increase in current. Is the effect of this transient current on the device consistent with the start-up time?

    Best regards,

    Ansel Song

  • 0 in reply to Ansel Song
    TI__Mastermind 23361 points

    Hi Ansel, 

    During continuous operation, for a load change, we normally refer that as load transient event. During load transient, since the output voltage is already up, during the load change, there could be undershooting voltage when applying the load and overshoot voltage when removing the load, but during this case, the voltage on the capacitor is already at the output voltage and the input current change is primarily the change on the load. 

    The in-rush, however, is the peak current during startup when charging the output capacitor from ground level and this will result in the much higher transient current. 

    There is an app note on this topic you may find helpful. 

    Regards, 
    Jason Song