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TPS62816-Q1: TPS62816-Q1 EVM Current capacity

Imelda Zhang
Expert 4305 points
Part Number: TPS62816-Q1

Hi Expert,

This is Imelda, FAE from China Auto Team.

My customer is using TPS62816-Q1 in their project. The TPS62816 can go to 6A, but the SW, PIN3, for this device is a very thin pad, resulting in a very thin IC-to-inductor connection. In theoretically, this is a bottleneck for overcurrent. 0.25-mm wire width, 1-oz copper thickness, and pad current capability of 1.267 A. The thickness of the paste (for example, taking 120 um) is calculated, and the pass capacity is 1.7 a, which is much different from 6 A.  How do we balance line width with overcurrent capability? Thanks a lot for your help!

  • 0
    TI__Intellectual 2040 points

    Hi Imelda, 

    Thanks for the inquiry. Could you please share your calculation method which was used for calculating the pass current capacity?

    Additionally, it would be helpful if you could explain the importance of this? Did the customer face any issues with the EVM? 

    Thank you. 

    Best Regards,

    Rameen

  • 0 in reply to Rameen
    Prodigy 130 points

    Dear Rameen,

             Thanks for reply！Calculation shown as below:

    I=K*T^0.44*A^0.75
    K  0.048
    T(temperature rise) 20 ℃
    A(cross section area)=Width*Thickness 13.56252713 mil^2 <= copper thickness 1oz 1.377953 mil
    width 0.25mm 9.84252 mil
    I 1.267505639 A
    0.25mm width，1oz copper thickness，current capability is 1.267A

            We'd like to know TPS62816 pin current capability when doing layout for this chip. Thank you!

    Best Regards,

    Michael

  • 0 in reply to Michael Huang
    TI__Intellectual 2040 points

    Hi Michael,

    I will get back to you regarding this tomorrow.

    Thank you, 

    Rameen

  • 0 in reply to Michael Huang
    TI__Intellectual 2040 points

    Hi Michael,

    I believe the current capability of the High side switch may be used as a reference since it can handle the maximum output current.

    Our PCB has been designed according to our specified rules, and we have tested the EVM board with the maximum output current and the waveforms can be seen in the datasheet, the device switch pin is capable of handling the maximum output current. For detailed board layout information, please refer to the "N-1229 SIMPLE SWITCHER® PCB Layout Guidelines," specifically Section 6.1 on Current Handling Capability. You can access the document here: 

    www.ti.com/.../snva054c.pdf

    Michael Huang said:
    We'd like to know TPS62816 pin current capability when doing layout for this chip. Thank you!

    To assist with the layout process, I recommend the resource "Five steps to a great PCB layout for a step-down converter." You can access the document here: 


    www.ti.com/.../slyt614.pdf

    Thank you.

    Best Regards,

    Rameen

  • 0 in reply to Rameen
    Prodigy 130 points

    Dear Rameen,

             Yes, according to the wave in the datasheet, we believe that SW and GND pin can support 6A in EVM design. Just one concern that according to " Section 6.1 on Current Handling Capability", only depending on 0.25mm pin width can't support 6A current. Traces close to SW or GND pin is wide enough to help heat dissipation may make sense, is it right? Thank you so much for your reply and valuable documents!

  • 0 in reply to Michael Huang
    TI__Intellectual 2040 points

    Hi Michael, 

    I will get back to you about this by the end of the day. 

    Thank you, 

    Best Regards,

    Rameen

  • 0 in reply to Michael Huang
    TI__Intellectual 2040 points

    Hi Michael, 

    Yes, the traces close to SW pin or GND are wide enough to handle the current/ heat dissipation in the EVM. 

    Michael Huang said:
    Traces close to SW or GND pin is wide enough to help heat dissipation may make sense, is it right

    Thank you. 

    Best Regards,

    Rameen