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TPS65150: LCD3.3V (TPS65150-G1) inrush current waveform (load LCD) is 4 segments. what is the specification of VGH/VGL maximum starting current~

Part Number: TPS65150

Hi,
As the title says, the picture is the result of the test.

Thanks in advance~

Thanks in advance

Aihua.

  • Hello,

    Thank you for your question. Today is a holiday in the US and I will review and provide my feedback by early next week.

    Kind Regards,

    Liaqat

  • Hello,

    Please see plot below for inrush current when various rails of TPS65150 power up. It is for conditions of Vin=3.3V, AVDD=15V, VGL=-9V and VGH=23V. Although cursor is only at position when AVDD is ramping up, measured peak inrush current when AVDD is ramping up is 1.1A, when VGL is ramping down is 900mA and when VGH is ramping up is 1.38A. I hope that this gives you an idea of the TPS65150 inrush current during start up.

    Kind Regards,

    Liaqat

  • Hi,

    Thank you for your reply, we tested it on a new prototype, as shown in the figure(overshoot appears at 70ms).
    What is the maximum input current value corresponding to chip VIN(LCD3.3V)?
     In addition, there are some other power-related problems, pls help to see if you have encountered and how to solve it.
    1.Temp.= -30℃,AVDD Io up (normal load → 100mA),AVDD Vmin= 13.13V(<13.2V)
    2.Temp.= -30℃,AVDD Io up slope (normal load → 100mA),AVDD Vmin= 13.06V(<13.2V)
    3.Temp.= -30℃,AVDD Io max= 100mA, AVDD Vp-p= 344mV()
    Thank you so much~

    Kind Regards,

    Aihua

  • The attached pictures correspond to the order of the questions, thank you

  • Hi Aihua,

    The current spike at ~70ms is likely due to a load condition and not inrush current due to initial charging of output capacitance.  You will need to debug this in the system because it is hard for me to understand what is causing it without having the system for me to measure. This could just be a normal operation of the system. Regarding your other questions, I am sorry but I am not fully clear on what the questions are. I think you are referring to increased ripple at the boost output when load is increased. Your last scope plot shows ~200mv ripple which seems high. I would suggest to add extra ceramic capacitors at the boost output to see if it reduces this ripple magnitude. Normally, ripple at boost output should be less than 50mv.

    Kind Regards,

    Liaqat

  • Hi Liaqat,

    Thank you for your reply.
    Screen manufacturers have been confirmed, and we will also confirm those low-temperature waveforms.
    What is the maximum input current value corresponding to chip VIN(LCD3.3V)?
    Thank you so much~

    Kind Regards,

    Aihua

  • Hi Aihua,

    Input current will depend on the load current and obviously will be higher for higher load current and lower for lower load current. As far as anything limiting the peak input current inside TPS65150, it is boost switch current limit. Specification for this boost switch current limit in the datasheet are:

    Minimum = 2.0A, Typical= 2.5A and Maximum = 3.4A

    So peak input current can be as high as 3.4A

    Boost inductor value, switching frequency (1020KHz  - 1389KHz) and load current will determine at what load current value the boost switch will hit this 3.4A maximum current limit but it will be somewhere approx. 700mA of load current.

    Kind Regards,

    Liaqat

  • Hi Liaqat,
    We continue to reproduce this problem and found that the inrush is related to the VCOM power-on in the screen.
    The inrush current is about 2A (as you said in the previous letter is normal), but TI’s chip input force 3.3V will drop to 2.5V, which is Does it meet the chip requirements?
    The current in the following two pictures is the same PIN
    Thanks.
    Kind Regards,
    Aihua
  • Hi Aihua,

    TPS65150 Vin specification is minimum Vin=1.8V so 2.5V is o.k. from input supply perspective. But since your input supply is not able to provide the needed load current and therefore dips,you may consider adding additional capacitance at the input supply. 

    Kind Regards,

    Liaqat

     

  • Hi Liaqat,

    Thank you for your support and help.
    Finally, we added a 47u capacitor to AVDD. After the improvement, the inrush=1.47A and the drop is almost gone,
    Thank you so much~

    Kind Regards,

    Aihua.