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TPS259230-41EVM: tps259230

Fab ML
Prodigy 50 points
Part Number: TPS259230-41EVM

Dear All,

I have on my power supply board an efuse, the TPS259230. I powered the device with 5.5V, setted the rampe time to 2ms trough a condensator of 33pF, and limit the current to 3A with a resistance of 82.5k. I would like to get in output a range voltage of 5V to 5.2V driving loads from 0 to 3A . The issue is that i can get 3A in output but the output voltage dicreases when the output current increases.

Does someone have any suggestions please ?

Thank you

Fab

  • 0
    TI__Guru 57737 points

    Hi Fab,

    What is the resistance in the path between Vout of TPS259230 and your measure point.

    Can you please share the schematic for this design. Also, please share waveforms at Vin, Vout (at TPS259230) and  Iin/Iout during loaded condition.

  • 0 in reply to Praveen GD
    Prodigy 50 points

    Hi Praveen,

    without any resistence load i get Vout = Vin and Iout =0A,

    When i connect 5ohm of load my Vout=5V and Iout=1A

    with load resistence 2,5ohm, Vout= 4,7V and  Iout= 1,8A.

    ....

    In all these measurements the Vin is still 5.5V

    So reducing the value of the resistence load , the Vout descreses (not normal) and the Iout increases till the setted limited current 3A . Above this, the device goes in protection mode.

    Thanks.

    ML

     

  • 0 in reply to Fab ML
    TI__Guru 57737 points

    Hi Fab,

    The resistance of the efuse, TPS259230 is expected to be in the range of 40 mohms  in steady state. From your  test results it looks like the resistance is around 500 mohms. The only possible scenarios I could think of are,

    • There is a resistance in the path between Vout and your measurement point (can happen due to connectors or long wires) as shown below.
    • Rilim is set to 82.5 kohms which corresponds to 3.175 A current limit. It can so happen that the Rilim is set to another value which corresponds to a lower current limit and  efuse is limiting the current and the VOUT drops as a result of current limiting.
    • The IC is damaged. Please try replacing the IC and test again. 

  • 0 in reply to Praveen GD
    Prodigy 50 points

    Hi Praveen,

    Thank you for the answers.

    Considering the first point i resolved the issue. More than the wire resistence i had put in serie in these two points a multimeter which also has an intern resistence; this could explain why i got these results before.

    Doing new measurement with these value: Rilim = 100k , Vin = 5.5V , Rload = 1,67ohm , Cout = 11uF , i got in output of the TPS Vout = 5.36V and Iout = 3,23A. Calculating the power dissipation on the mos of the TPS  i find a value approximately the fortieth of the total power dissipated and not the sixth as written in the datasheet.

    Could you please give an explanation to this fact?

    Thanks,

    Fab.

  • 0 in reply to Fab ML
    TI__Guru 57737 points

    Hi Fab,

    With a load current of 3.23A,

    • The voltage drop across the internal FET = I x R = 3.23 A x 40 mohms = 0.13 V
      • Vout = Vin - Drop = 5.5V - 0.13 V = 5.37 V
    • Power Dissipation in the FET = I^2 x R = 3.23^2 A x 0.04 mohms = 0.417 W

  • 0 in reply to Praveen GD
    Prodigy 50 points

    Thanks Praveen, it is clear.

    Regards,

    Fab