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TLV707: Inrush current spike at boot-up phase

Dave Chang
Expert 3935 points
Part Number: TLV707

Hello support team,

This is FAE Dave, thanks for taking time looking into this issue.

Figure.1 is the limit listed in datasheet and it states that the limit is 450mA of the maximum.

Fig.1

My customer has experienced the current spike during the boot-up, as the figure.2 and figure.3 below.

Fig.2 and Fig.3

Output VR MLCC

1uF*1

Output Device MLCC

22uF*4+47uF*2+0.1uF*2

IIN(fig.2)

1.05A

Pd (instant)

(3.3-1.8V)*1.05A=1.575W

 

Output VR MLCC

1uF*1

Output Device MLCC

22uF*1+0.1uF*2

IIN(fig.3)

932mA

Pd (instant)

(3.3-1.8V)*0.932A=1.398W

My customer has provided me the schematic, if it is needed, I could sent it through email.

Thanks for the support!

Best regards,

Dave

  • 0
    TI__Expert 5291 points

    Hey Dave, 

    It looks like the LDO is hitting current limit. The LDO takes sometime for the current limit to kick in, it's not instantaneous (hence why this 1A spike is happening). When you are reducing the Cout this is slowing that inrush. Is it possible to make Cout the minimum capacitance specified in the datasheet? Keep in mind this will have some tradeoff with transient response. Another option would be to keep the Cout caps and if the things around the LDO can handle this inrush current and are robust, then the LDO should be able to survive this event without harming it. 

    Yes, please send schematic through my email as well and I can review it. 

    Thanks, 

    McKyla

  • 0 in reply to McKyla Beuttler
    TI__Expert 3935 points

    Hello Mckyla,

    I've sent the schematic to your mail.

    Thanks for the support!

    Best Regards,

    Dave

  • 0 in reply to Dave Chang
    TI__Expert 5291 points

    Hey Dave, 

    Schematic can be discussed over email. Please see app note: Managing Inrush Current App Note let me know you have additional questions related to inrush current. 

    Thanks, 

    McKyla