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TPS65105 is not working

Vijay Anand
Prodigy 160 points
Other Parts Discussed in Thread: TPS65101, TPS65105

Hi,

We are using TPS65105RGER in our design for a LCD Display voltages like 10V, 19V, -7V5, 3V3, VCOM.  But we have not seen any switching pulse in pin 8 and 9.

We have observed that 1.23V ref is coming out in pin 23 and also 3.3V alone working.  here is my circuit. 

Please share your feedback for the same. Still we need to get the other voltages like 10V, 19V, VCOM and -7V5. 

Thanks in advance,

Vijay

  • 0
    TI__Guru 65310 points

    Hello Vijay,

    Would it be possible that you send a scope shot of the startup? I wonder if the part does not start at all or if it tries to start and the protection kicks in. If the protection kicks in, please check if there is one output voltage that drops in voltage after all voltages reached already their final value.

    Another test would be to check with TPS65101 if the problem is gone. This is the same part, just the boost converter has more current and the protection is not present, so it could be used to check if one of the output voltages falls out of regulation and which one.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 160 points

    Hello Briitte,

    As you told TPS65105 is starting and it get shut down. It is because of the over current at the load? But we have not connected any load to this to any of IC's voltage rails. 

    Please find the Startup here.

    Expecting your reply

    With Regards,

    Vijay

  • 0 in reply to Vijay Anand
    Prodigy 160 points

    Hello Britte,

    We have soldered TPS65101 as you suggested, now we are getting the required voltages.  Thank you for  support.

    With Regards,

    Vijay

  • 0 in reply to Vijay Anand
    TI__Guru 65310 points

    Hello Vijay,

    To be honest, this was meant as a test, not as a solution :-)

    If there is no load attached and the part still goes into shutdown, I expect that one of the converters is not stable and I expect as well that it is the boost converter. Please check the stability of the converter as described in the datasheet because the part should start properly when no load is connected otherwise you might get into trouble in mass production.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 160 points

    Hello Brigitte,

    You are right.  Could you please help me what is the reason for shut down when there is not load connected. Is it because of  Cap an Res which might get wrong in the assembly ? or Inductor or diode selection ?

    With Regards,

    Vijay

  • 0 in reply to Vijay Anand
    TI__Guru 65310 points

    Hello Vijay,

    Most probable the boost converter is instable. When checking the scheamtic, it seems that there is just a very small output capacitor. Is this correct? If yes, please add a bigger output cap and check if the problem is gone.

    Best regards,
    Brigitte