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TPS2663: EFUSE TPS26632 doesn't work at 10V Vin

sreeroop a
Prodigy 60 points
Part Number: TPS2663

Hi,

I am attaching my TPS26632 Efuse circuit schematic. Right now my circuit doesn't work at 10V. If I bypass the efuse , the circuit works normally.So something is limiting the efuse to not work at voltages less than 11V.

My device conditions are :

Under voltage : 9.5V Min

Operating voltage: 10V

Max voltage :35V

Max Inrush current : 3A

Current limit : 5 A

Power limit : 62 W

Cout =129.2 uF

I have replaced a few resistors with new values to make it work at lower voltages. So right now these are the values that I am using , but still it doesn't work at 10V during a cold start. Could you please let me know the changes to be made to make it work at 10V?

PLIM : 62K ohm (62 W)

ILIM: 3k ohm (6A)

UVLO : R1- 750k ohm, R2- 150k ohm (7.2V)

CdVdT: 10nF

Thank you

Sreeroop

Behavior of Efuse at 10V input and 7.5 ohm load is as follows: 

  • 0
    TI__Guru** 105361 points

    Hi Sreeroop,

    Welcome to E2E!

    Somehow your images are not showing up. Can you repost them ? Can you share startup test waveform with UVLO, input current, Vin and Vout

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 60 points

    Inrush current of 1.8A at startup at 10Vin

  • 0 in reply to Rakesh
    Prodigy 60 points

    Hi Rakesh, 

    Thank you for responding. 

    I am really sorry, I don't have the equipments right now to share the startup test waveform. 

    Could you please help me to find the required resistor values to make it work according to device conditions as specified above? 

    I have opened up all the tabs, increased the current limit to maximum, i.e 6 amps, No power limiting, Undervoltage lockout set to 7V and changed the dv/dt capacitor to 10nF which is its minimum recommened value and still it doesn't work at 10V input. 

    I also have noticed that when I change the dV/dT capacitor to 1nF to allow more inrush current, circuit is working fine. But since it is below it's recommended minimum value can I do that? Could you please advise?

    Thank you 

  • 0 in reply to sreeroop a
    TI__Guru** 105361 points

    Hi Sreeroop,

    Looks like the start load with slow ramp is causing the device to thermal shutdown.

    Is it starting with only Cout and without R-load ?  or with only R-load and without Cout ?

    What is the actual load ? Is it working fine at 10V when interfaced with actual load ?

    Startup test waveform with UVLO, input current, Vin and Vout would help to debug.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 60 points

    Hi Rakesh, 

    Is it starting with only Cout and without R-load ?  or with only R-load and without Cout ?

    It's starting with Cout and with a load. 

    What is the actual load ? Is it working fine at 10V when interfaced with actual load ?

    Actual load is a 7.5 Ohm Electronic load, when I bypass the efuse the circuit is working fine at 10V input and with the 7.5 Ohm load. When Efuse comes into play then it doesn't start at 10V anymore. 


    Please let me know if you need anymore details.

    Thank you

    Sreeroop

     

     

  • 0 in reply to sreeroop a
    TI__Guru** 105361 points

    Hi Sreeroop,

    I meant your end load. In your initial post you already mentioned about using 7.5 ohm load

    Is it starting with only Cout cap and without 7.5 Ohm Electronic load ?

    Is it starting with only 7.5 Ohm Electronic load and without Cout cap ?

    Please provide startup test waveform with UVLO, input current, Vin and Vout to debug.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 60 points

    Hi Rakesh, 

    It is starting with Cout cap and without 7.5 Ohm electronic load. 

    I am really sorry, I don't have an osciloscope right now with me to provide you with the startup test waveform. 

    Also can I use a 1 nF capacitor for dV/dT ? it is below it's recommended value. Is it fine?

    Thank you

    Sreeroop

  • 0 in reply to sreeroop a
    TI__Guru** 105361 points

    Hi Sreeroop,

    You can use 1nF for dV/dT or even leave dV/dT pin OPEN.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 60 points

    Hi Rakesh, 

    Thank you for replying.

    using 1nF for dV/dT will solve my issue .

    Thank you & Best regards 

    Sreeroop