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TPS22944: datasheet Fig 20 and Fig 21

Steve Wenner
Genius 3190 points
Part Number: TPS22944

Good afternoon...

I am trying to understand the Vout on Fig 20 and 21....In particular the Vout when the current exceeds the current limit goes into an intermediary stage (~1.2V  or so)......Is this the UVLO that is called out within the datasheet?  I am not able to discern this for sure and have always been under the impression UVLO is a lockout when Vin dips too low.....

Thanks 

Steve

  • 0
    TI__Genius 10855 points

    Hey Steve,

    You are correct, UVLO occurs if the input voltage drops below a specified voltage level. 

    Regarding Figure 20 and 21, these figures are demonstrating the tblank response and trestart response when responding to an over-current event. In Figure 20, the output is "soft" shorted to GND, instead of hard shorted. This ensures that the overcurrent behavior is captured without the device entering thermal shutdown.

    In Figure 21, the short is causing the device to enter thermal shutdown and retry. In this case, the device is cycling in and out of thermal shutdown. 

    Thanks,

    Arthur Huang

  • 0 in reply to Alpha H
    Genius 3190 points

    Hi Arthur....

    thanks for the response!.....

    So just so I'm clear....When the device either over currents due to excessive load, thermal shutdown or UVLO, the output voltage drops to some level such that the excessive output current and output voltage  produce a maximum output power which holds steady until the shutdown occurs?  Basically the Vout has three states...On, Off and some in between???  Trying to make sense of the in-between.....Guessing it's value is power dependent which in turn really is determined by the amount of excess current draw from the part.....

    Thanks

    Steve 

  • 0 in reply to Steve Wenner
    TI__Genius 10855 points

    Hi Steve, 

    This is correct, depending on the loading condition (hard short, start into short, soft short) the behavior of the device will  clamp the current by reducing VOUT. If the device enters thermal shutdown during this time, then the device will turn off and restart. 

    Thanks,

    Arthur Huang