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TPS1663: Question about PLIM

Part Number: TPS1663
Other Parts Discussed in Thread: TPS2663

Hi 

We would like to use TPS16632 in the pre-charge circuit to limit the output current at 6A . 

In order to achieve that, I should utilize PLIM feature. Am I right? 

If I keep the output current at 6A, then what will be temperature? Does it depend on the on-resistance like what has shown in the DS? Thanks.  

  • Hi Jack,

    we can precharge large capacitive loads using TPS1663/TPS2663 as the device automatically enters into thermal regulation loop. Please refer Reliable Start-up with Large and Unknown Capacitive Loads 

    Best Regards,

    Rakesh

  • Hi Rakesh, 

    Thanks for the reply. 

    Please allow me to clarify my question a little bit. Since the purpose of using TPS16632 is to limit the charging current, which I believe using PLIM to limit the output current at 6A. However, the only concern that we have is the heat. Would the continues 6A output trigger the thermal shutdown? 

    One more question. Which the mechanism TPS16632 is using to limit the output current? by internal MOSFET? Or it limits the output by power, not by current? Because we were not able to tell from the below internal diagram. 

    Thanks. 

    Jack

  • Hi Jack,

    PLIM comes into action only in steady state and not during startup. During startup, the inrush current can be limited by slew-rate control (refer section 9.3.1 Hot Plug-In and In-Rush Current Control in the data sheet) or thermal regulation loop (9.3.1.1 Thermal Regulation Loop). As both these methods heats the device, there is a chance of hitting thermal shutdown.

    Best Regards,

    Rakesh

  • Thank you, Rakesh. 

    It seems like TPS16632 might not work for the pre-charge purpose, because just like what you have mentioned, both modes (PLIM or overload) could eventually hit the thermal shutdown. Or we have a way to dissipate the heat? 

    Jack

  • Hi Jack,

    Few questions on the requirements..

    How much cap you need to charge and do you have any charging time constraint ? what is the operating voltage and end application

  • Hi Rakesh, 

    The application is for e-bike. Other info. I need to check and get back to you. 

    One question that I asked previous was that  how TPS16632 limit the output current? by internal MOSFET? We can see the current sense in the internal diagram, but not sure how TPS16632 limit the output current. Thanks. 

  • Hi Jack,

    Thanks.

    TPS16632 measures the load current and output voltage. The device multiplies these two to get the output power and then compares with the reference set at PLIM to regulate the internal FET to limit the output power.

    For pre-charging the output capacitor in these kind of applications, TPS48111-Q1 is suitable. Please refer the data sheet application example.

    Best Regards,

    Rakesh