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TPS61046: Question on TPS61046 inrush current

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Replies: 6

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Part Number: TPS61046

Hi TI Experts,

We are developing a boost converter circuit using TPS61046 which powers an OLED display. Refer below circuit for reference. We observed that as soon as EN is driving high, inrush current draws by TPS61046 can go as high as 560mA. We would like to know if this is the typical inrush current rating we are expecting? Is there any way to restrict the inrush current, as we would like to reduce it to about 200mA?  By means of experiment, we tried to modify the inductor value by changing its value from 10uH to 1uH, the inrush current can be limited to 260mA at power up. Do you suggest the act of changing the inductor value? Will it impact the system stability? Thank you.      

VBAT:3.8V

Vout: 9V @ 20mA

L5 inductor:10uH±10%/0806/DCR:1.2ohm/current rating:225mA 

C29:4.7uF±20%/0603/X5R/16V

  • Dear sir:
    When the converter is enable, it will charge the Cout to the target. So it will cause large current even with light load. The larger Cin, smaller inductance and smaller Cout may do help. But you need to do load transient test to check if the Vout is stable and no large ripple.

    We also have an application note for similar usage. May it do some help for you. www.ti.com/.../slva307b.pdf

    Best Regards

    Minqiu

  • In reply to Minqiu Xie:

    Additionally, please disable the load before the converter finishes startup.

    Best Regards

    Minqiu

  • In reply to Minqiu Xie:

    Hi Minqiu,

    I studied the application note - slva307b, which provides a way to adjust soft start time in order to reduce inrush current. However, the method described is applied to TPS61070. Does it also applicable to TPS61046? Besides, I also attempted to change inductor value from 10uH to 1uH, and noticed that inrush current reduces significantly. Do you think it is a good idea to modify the inductor value in order to minimize inrush current? Will it introduce instability to the system? Thank very much.

    Best regards,

    Peter    

  • In reply to Hoi Wa Ip:

    Hi Hoi Wa Ip:
    The application is suitable for TPS61046 just care about the FB voltage shouldn't larger than 1.2V during the startup.

    Yes, change the inductance is a good choice. You could do load transient test to check if the system is stable.

    Best Regards

    Minqiu

  • In reply to Minqiu Xie:

    Hi Minqi,
    Thank so much for your help. One more question -would you mind to explain why does decreasing inductance value can effectively reduce Inrush current?

    Best regards,
    Peter
  • In reply to Hoi Wa Ip:

    Hi Peter:
    Assume the peak current limit is a constant value, then the average current will be Ipeak-0.5*ΔI. And the ΔI is influenced by the inductance mainly. Smaller inductance will bring larger current ripple, so the inrush current will be decreased.

    Best Regards

    Minqiu

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