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TPS92692-Q1: SS and FLT pin

Ivy Jin
Expert 4625 points
Part Number: TPS92692-Q1

Tool/software:

Hi team,

Customers need to implement both the Hiccup Mode Short-circuit Protection and the MCU detect FLT pin status. 

May I know if it is possible to connect SS to FLT directly and pull up to 5V MCU-VDD via 100Kohm (MCU-VDD is the LDO output of their MCU). Is this any risk to the SS pin? 

Regards,

Ivy

  • 0
    TI__Expert 5790 points

    I'm not really sure what you intend on doing here as the FLT pin is an nFLT which is high during normal operation and low during fault conditions.... why would you attach this pin to a voltage source? What would that achieve with respect to the micro? 

    This is the correct way to interface with the FLT pin



  • 0 in reply to Daniel Louis
    TI__Expert 4625 points

    Hi Daniel,

    The customer would like to pull up the FLT pin to 5V as it is the OD state,  this is the same as pulling the FLT pin up to the Vref pin.

    Now they want to use the hiccup mode short circuit protection, but when designed as shown in Figure 34 or 35, they think their MCU cannot disable the SS pin in time (they have a software filter). Therefore, they want to pull down the SS pin using the FLT pin in a fault condition. With this in mind, they connect SS and FLT together and pull up to 5V.

    They want to know if there is a risk to design this way. 

    Regards,

    Ivy

  • 0 in reply to Ivy Jin
    TI__Expert 5790 points

    Hi Ivy,

    Yes, you can do that.

    but keep in mind that in that configuration, the soft start ramp will no longer be linear since your voltage source will now be contributing to the SS ramp up and, therefore, it will also effect the soft start ramp time. 

    Regard,
    Daniel

  • 0 in reply to Daniel Louis
    TI__Expert 4625 points

    Hi Daniel,

    Consider the soft start function, they want to use the following design (FLT pulls the SS pin down by 2 NMOS, voltage source will not be contributing to SS pin ), they think it will better than SS and FLT connect together. 

    What about your suggestion?

    Regards,

    Ivy

  • 0 in reply to Ivy Jin
    TI__Expert 5790 points

    Looks great!