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TPS2490EVM-001: External driver to increase driving capability of TPS2490

chee hua how
Prodigy 60 points
Part Number: TPS2490EVM-001
Other Parts Discussed in Thread: TPS2490

Tool/software:

Dear Sir/Madam;

 

I am using TPS2490EVM-001 board to evaluate TPS2490 hot-swamp controller, operating current needs to be as high as 50A.

For such reason the pass element MOSFET is changed from IRF540NS to BUK7Y1R0-40N (´3)

As the input capacitance of BUK7Y1R0-40N is relatively higher than IRF540NS the charge pump driver of TPS2490 didn’t seems be be sufficient to drive the BUK7Y1R0 MOSFET.

Under such situation do u have any recommendation of external discrete driver configuration or driver IC that i can use in between TPS and the MOSFET?

Thanks

  • 0
    TI__Mastermind 42380 points

    Thanks for reaching out. We don't recommend any external driver circuit. Did the TPS2490 controller not power up? Hot-Swap controllers are designed to power up with a lower output voltage slew rate to limit the start-up inrush current. Hence, the gate drive is limited to a lower value. 

     

  • 0 in reply to Avishek Pal
    Prodigy 60 points

    Thanks for answering, No TPS2490 can't activate BUK7Y1R0-40N (*3 in parallel) at all. if I reduces the mosfet to a single BUK7Y1R0-40N it is hiccupping

  • 0 in reply to chee hua how
    TI__Mastermind 42380 points

    Are you using the TPS2490EVM to place three (3) BUK7Y1R0-40N MOSFETs? The TPS2490EVM has a provision for only one MOSFET. How are three MOSFET are populated? 

    Please list down the changes made on the EVM schematic is any. Otherwise, please share the schematic. 

    Please share the start-up waveforms.

    VIN, VOUT, GATE, TIMER, and Input Current need to be captured in a single scope shot. 

  • 0 in reply to Avishek Pal
    Prodigy 60 points

    Hi Avishek Pal

    Basically I have three of BUK7Y1R0-40N soldered on a separate board and on the TPS2490EVM I removes its IRF540 MOSFET and jump three wires to the MOSFET board.

     

    I am tight with other work at the moment once I have more time I will probe the waveform u mentioned and put it here.   

  • 0 in reply to chee hua how
    Prodigy 60 points

    Hi Avishek Pal

    Finally I managed to get back into this issue two week ago, I am modifying TPS2490EVM board to meet my requirement.

    Input voltage: 26V

     

     R1=680k, R2=68k, R4=110k,

    C3=10nF, C4=4n7, C5=10nF, C1=100uF

    R5=560uR @ 3W

    Q1=PSMN1R5-30BLE (´2)

     

    To accommodate two D2PAK into the EVM I uses sand paper to remove portion of the solder mask and realign Q1 position such that I can squeeze and solder two of them as shown in the attached picture.

     

    With the development work I managed to get it working this time here is the waveform (F12(g) & F12(h)) when startup with a load with 13mF input capacitance.

    F17(e) is the waveform when I perform a hot-short at the EVM’s output, IO spikes up to about 182Apk during the hot-short moment.:

    • VGSQ1 drops to about 3V.
    • VDSQ1 raised to about 29V.

     

    Both (a) & (b) above indicating that Q1 is forced off however VTimer remains low during that transient period.

    VTimer takes a 6.4ms delay before it start charging up.

    My question since VTimer not even start charging what is the protection mechanism that kick-in to momentary disabling Q1 in the first short pulse immediately after the hot short?  

     TPS2490EVM questions.pdf

  • 0 in reply to chee hua how
    TI__Mastermind 42380 points

    If the load current increases rapidly (for example, the load is short-circuited) the current in the sense resistor (RS), Q1 is quickly switched off by the 125mA (typical) pulldown current at the GATE pin. There is a fast comparator to detect the rapid increase in current flowing through the current sense resistor, whose response time is 1.2 μs (max).

  • 0 in reply to Avishek Pal
    Prodigy 60 points

    Hi Avishek Pal

    Thanks for that it seems that that feature is neither shown in the block diagram nor in the feature description of the IC. But in the specification under GATE sinking current it do shown that V(VCC-SENSE) >= 200mV, IGATE= 125mA.

    On there other section TF_TRIP(@V(VCC-SENSE):0 -> 200mV) = 1.2us

    That clear my doubt, yes I think I have no more issue. Thanks a lot for your help, I will close the case.