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TPS65132A :the output capability of OUTN and the current limit

Jerrison Wang
Prodigy 80 points

 

TPS65132A0YFFR is used with a panel ( driver IC PN is NT35596), There is a 120mA with 170us pulse on OUTN when the power on or power reset, --pls see the attached waveform.

question are

1 if  OUTN can support 120mA /170us pulse , the output cap is 4.7uF

2. what is the value of the current limit for OUTN ?

3. what is the time to trigger the current limit of OUTN?

Thanks

 


 

  • 0
    TI__Expert 8010 points
    Hello Zhen Wang,

    The waveform shows the soft start-up ramp of the negative charge-pump (CPN). The CPN integrates a soft-start that ramps up the output voltage (VNEG) within a time defined by the selected mode.
    For the TPS65132A the start-up current in smartphone-mode is 50 mA, in tablet-mode is 100 mA (typical). Comparing the waveform with the mode characteristic would result that your customer's application is set for tablet mode? If this is the case, than the output current capability is 80 mA (min.) and the start-up current can shortly raise to the given value. I do not see anything suspicious here.
    What are the current limitation of the panel? Do they have problems with the start-up current of the A- Version.
    You can look up the Power-Up And Soft-Start (CPN)- Description in the d/s (chapter 8.3.5.2), there you will get more information about the start-up behavior of the different versions.

    Thank you.
    Best Regards,
    Ilona
  • 0 in reply to Ilona
    TI__Prodigy 80 points

    Ilona

    Thanks for your answer

    as customer found that the pulse  (which is caused by the driver IC of the pannel )120mA/170us  occurred in the OUTN when the TPS65132A had worked after power on. it had exceed the 80mA,and it is not mentioned the maximum current in the datasheet

    1.So as the time is short(170us) for the 120mA pulse , TPS65132A can support this pulse?

    2.I do not find the OCP value of the charge pump OUTN, could you pls help to provide the OUTN's current limit value and the the curent limit trigger time?

    Thanks

  • 0 in reply to Jerrison Wang
    TI__Expert 8010 points
    Hello Zhan,

    The device does not have a latched- OCP behavior. This means that at the moment when the overcurrent (>80 mA) is detected the device will be turned-off, but as soon as the current has decreased then it will regenerate and start-up again.
    In terms of the elevated output current of 120 mA at the panel this would mean that the output voltages drops for a period of 170 us.
    How much voltage drop on the output do you see during the start-up? Does the customer see a problem with that?

    Thank you.
    Best Regards,
    Ilona
  • 0 in reply to Ilona
    TI__Expert 8010 points
    Hello Zhan,

    Do you have any feedback on this?

    Thank you.
    Best Regards
    Ilona
  • 0 in reply to Ilona
    TI__Prodigy 80 points

    Ilona

    Thanks for your help , I have sent email for you for the update