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TPS24751: The lowest current limited of TPS24751

kevin p
Intellectual 470 points
Part Number: TPS24751
Other Parts Discussed in Thread: TPS2595

Hello team,

I want use TPS24751 on my hot swap product, I have some issues ,please help to confirm,due to the new product need to design, please help to review follow issues ASAP.

1. The input voltage is 3.3V, the input current  is 0.3A,  i want to control the inrush current, the inrush  current is 0.3A, does TPS24751  meet the hot swap requirement？

2.  On the datasheet, High ILimit Accuracy from 10 mA to 12 A, what's the lowest current can be Limited? 10mA or others? if  the input voltage on the TPS24751  is 3V, the input current is 0.1A,  does TPS24751 work normal?

Look forward to your reply, thanks.

kevin

  • 0
    TI__Guru** 103436 points

    Hi Kevin,

    Thanks for reaching out!

    TPS24751 supports input voltage starting from 2.5V and current limit setting from 10mA. It will meet your requirement.

    Can you share your use case and end product details.

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Intellectual 470 points

    Hi Rakesh,

    Thanks for your support.

    I will use TPS24751 on a plug module. The main function is to monitor industrial data such as temperature, humidity, data transmission error, etc.

     

    The input voltage is 4.7V~5.3V, the max power is 4W, and the inrush current is less than 1A.

    Attached is the block diagram of the hot-swappable power supply. Please help to review and give your comments.

     

    I use the TPS2475x_Design_Calculator, I have some confuse, please help to clearfy.

    1.

    RLOAD-start

    Resistive load present at start up (not recommended)

    How to evaluate the RLOAD-start in my application?

    2.

    CLOAD

    Output load capacitance

    The output load capacitance is 150UF on the output of TPS24751, and there are DC/DC, LDO in the circuit, Is the load capacitance of DC/DC and LDO also add to the CLOAD ?

    3.

    Iramp

    Choose output capacitor charge current (<Plim/Vccmax)

    How to evaluate Iramp?

    Look forward to your reply, thanks.block of power.pdfTPS2475x_Design_Calculator_LowVin_5V.xls

    kevin

  • 0 in reply to kevin p
    TI__Guru** 103436 points

    Hi Kevin,

    TPS2595 looks more appropriate fit for your target specification. The input voltage is 4.7V~5.3V, the max power is 4W.

    Please check TPS2595 and let me know. If you wish to proceed with TPS24751, I will go through the attachments.

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Intellectual 470 points

    Hi Rakesh,

    Thanks for your support.

    I want to use TPS24751,please help to review and give your suggestion

    Thank you.

    kevin

  • 0 in reply to kevin p
    TI__Guru** 103436 points

    Hi Kevin,

    1A) RLOAD-start refers the equivalent load during startup. If your downstream load is DC-DC, we suggest to use PG output of TPS24751 to enable the DC-DC converter so that the load on TPS24751 device is just only the capacitive load 150uF.

    2A) All the load capacitance connected at the output of TPS24751 should be taken into account.

    3A) Iramp is the current determined by the GATE slew rate which can be adjusted by the Rext, Cext values at the GATE pin. For your 150uF, you can leave GATE pin open.

    Please refer the attached modified design sheet.

    • Leave Rext, Cext OPEN
    • Use 47nF for CT

    modified_TPS2475x_Design_Calculator_LowVin_5V.xls

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Intellectual 470 points

    Hi Rakesh,

    Thanks for your support.

    I updated the C_load,added the LDO output capacitance,the C_load is 400uF, so I need to control T_dv/dt, how to confirm  the C_gate,R_gate and the resistor of Prog?

    By the way, the CT is more than 98.2nF from the result of design calculator tool,  and  the  SOA  Pass  is "No", 

    I updated the design calculator  as attached, please help to review and give your suggestion.

    Look forward to your reply, thank you.

    kevin

    modified_V2.0_TPS2475x_Design_Calculator_LowVin_5V.xls

  • 0 in reply to kevin p
    TI__Guru** 103436 points

    Hi,

    What is your inrush current limit target ? Is it 0.2A.? Can we increase ? If not -why ?

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Intellectual 470 points

    Hi Rakesh,

    Thanks for your support,

    The inrush curent is 0.85A,thank you.

    Kevin

  • 0 in reply to kevin p
    TI__Guru** 103436 points

    Hi Kevin,

    Then Iramp can be set to 0.85A, which decreases the startup time and CT value to help increase the SOA. However, this design able to start load from 6 Ohm. If you want to start from 5Ohm, you need to increase inrush current and current limit.

    I suggest to use PG output of TPS24751 to enable the DC-DC converter so that the load on TPS24751 device is just only the capacitive load.

    Best Regards,

    Rakesh

    modified_V3.0_TPS2475x_Design_Calculator_LowVin_5V.xls

  • 0 in reply to Rakesh
    Intellectual 470 points

    Hi Rakesh,

    Thanks for your support.

    There is no 6.8k resistor on my hands, can I replace it by 8.06K for the R-PROG?

    BTW,I find the threshold voltage on the EN is 1.2~1.4V and on the OV is 1.25~1.45V in the datasheet,

    In the calculation formula of the datasheet, VOVTHRESH = 1.35 V and VENTHRESH = 1.35 V.

    Does the threshold voltage is for all input from 2.5~18V application? The input voltage is 4.7~5.3V in my application, do you have any suggestions about these two thresholds on EN and OV?

    Thank you

    kevin

  • 0 in reply to kevin p
    TI__Guru** 103436 points

    Hi Kevin,

    It looks ok to use 8.06K for R-PROG.

    The EN, OV thresholds does not change with Vin. The typical values are used for calculations.

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    TI__Guru** 103436 points

    Hi Kevin,

    If you do not have any further questions, can you close this thread as resolved.

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Intellectual 470 points

    Hi Rakesh,

    Thanks for your support.

    Kevin