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TPS25944A: request schematic review

TS Yang
Genius 4800 points
Part Number: TPS25944A

Hi,

Please let me know whether there's any potential problem on below schematic.

1. OVLO/OVP : 4.6V~5.7V

2. Current Limit : 2.1A

TPS25944A_SCH_REV01_20180221C.PDF

thanks,

TS

  • 0
    TI__Guru** 105611 points
    Hi TS,

    Thanks for reaching out!. Following are the inputs on schematic.
    OVLO/OVP are configured correctly.
    DMODE pin 1 should be connected to GND.
    To set current limit at 2.1A; choose R44 and R56 values as 42.3 k ohm
    Is input reverse polarity protection needed? If no - D6, D9 can be removed.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Genius 4800 points

    Hi Rakesh,

    thank for your comments.

    I think that the design calculation tool of TI homepage is slightly different from the calculation.

    TPS2594x-Calculation Sheet V1p0_PM550-SEC_1.xlsx

    OVLO/OVP are configured correctly.

    -> I have applied the EVM Board Value, but there is a difference in the TI Excel file. Please let me know which one is better.


    DMODE pin 1 should be connected to GND.

    -> thanks, I'll update the schematic.


    To set current limit at 2.1A; choose R44 and R56 values as 42.3 k ohm

    -> TI Excel Calculation Tool has 35.7K Ohm. Please check which one is right.


    Is input reverse polarity protection needed? If no - D6, D9 can be removed.

    -> Yes, I want to use input reverse polarity protection for this circuit.

    thanks,

    TS

  • 0 in reply to TS Yang
    TI__Guru** 105611 points
    Hi TS,

    -> Regarding OVLO/OVP calculations.
    There is difference in EVM user's guide and design excel calculation approach. EVM user's guide considers "VIN Operational Range" which the board works. So, while calculating UVset, EVM user's guide considers rising threshold (V(ENF) = 0.99V) where the device starts working. But excel sheet is designed for UV_cutoff (V(ENF)=0.92V), the device turns off.
    I recommend to use excel sheet and modify value of R2 in row 23 to arrive at desired UV_final, EN_final values in rows 26 and 27 respectively.

    -> TI Excel Calculation Tool has 35.7K Ohm. Please check which one is right.
    2.1A is the design input for the Maximum continuous load current. The current limit target value (Ilimit) is calculated as 20% higher than Maximum continuous load current --> 2.52A in row 14. So, 35.7K Ohm sets current limit at 2.49A.

    Please let me know if you have any further questions.

    Best Regards,
    Rakesh