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TPS25983: current limit function

Niv Shalom
Prodigy 20 points
Part Number: TPS25983

Tool/software:

Hi,
I am writing to seek assistance regarding an issue I have encountered with the  TPS25983xL e-fuse IC, which I am using for under-voltage (UV), over-voltage (OV), and current limiting protection.

Retry_dly= open

Nretry= short to gnd

Itimer= open

Rlim=300R =5A

Cdvdt=100nf

While testing  the active current limiting function using e-loader , The e-fuse works as expected without a load connected. However, when I apply the load and reducing the resistance, the current exceed the 5A  current limit and rising till it reach 5.85A and then the efuse shut down.

what can I do to to fix this issue ?

thank you,

Niv

  • 0
    TI__Mastermind 26830 points

    Hi Niv,

    Can you confirm you are using CR mode of e-load. If not, can you try with that?

    There will be some variation between the devices (although the current in your case is slightly higher than the expected variation)

    Can you share exact test setup and method you are using?

    Best regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 20 points

    Hi Arush,
    Thank you for the reply.
    I've tested the current using CR and CC mode using "PRODIGIT 3311f" e-loader ,the current is still exceeding the 5.66A reaching 6A and then cut off.the e-Fuse have Reverse current blocking Using external FET and 10UF and 1Uf  capacitors on the out put signal. 

    B.R

    Niv

  • 0 in reply to Niv Shalom
    TI__Mastermind 26830 points

    Hi Niv,

    How are you monitoring the current? Are you using current probe or using IMON pin.

    Also do you have any waveforms?

    Is this repeating with multiple devices or at different ILIM values? During which stage of development are your seeing this issue?

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 20 points

    Hi Arush, 
    The e-loader monitor the current and the voltage on the load.
    The product has the same circuit on different outputs, repeating the issue and the results ,the product is in it's integration and testing stage.
    when replacing Rlim to 348R the current cutoff at 5.3A . 

    while testing this phenomenon, as I increase the current I can see the output voltage drop from 16.0V to 14.8  and then it cutoff (with Rlim=300R or Rlim=348R).

    I can replace Rlim to make the cutoff current low enough to reach the desired max current while the output voltage dropping but why the active current limit doesn't regulate it?

    Thank you,
    Niv

  • 0 in reply to Niv Shalom
    TI__Mastermind 26830 points

    Hi Niv,

    Niv Shalom said:
    while testing this phenomenon, as I increase the current I can see the output voltage drop from 16.0V to 14.8  and then it cutoff (with Rlim=300R or Rlim=348R).

    When the current drawn by the load increases, the device will regulate the current. During this time, the output voltage will become ILIM*R_load. Are you sure this isn't happening here? 

    During this regulation, the power dissipation will be higher (Vin-Vout)*ILIM so junction temperature will rise and this will result in thermal shutdown of the device. If you want the device to go into cut-off when the overcurrent limit is exceeded, use TPS259830O variant which have circuit breaker response instead of current limiting response.

    Do you have any waveforms which can help in confirming if the device is not regulating the current? Or is it possible for you to test on the TI EVM for this device.

    Best Regards,
    Arush