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TPS1H100-Q1: Request for Schematic and PCB layout review

Jeffrey Chung1
Genius 3280 points
Part Number: TPS1H100-Q1

Hi TI Team,

There was a burnt issue of TPS1H100AQPWPRQ1 on my customer board. So they are trying to change their schematic and PCB layout like attached files to improve this issue. I'd like to request the schematic and layout review. And they are considering to use the GND network(No.1) or external free-wheeling circuitry(No.2). Please check that and let me know the review result.

Schematic of TPS1H100AQPWPRQ1.pdf

2870.PCB layout.pdf

Regards,

  • 0
    TI__Genius 16390 points

    Hi Jeffrey,

    The schematics look good. However, I can't locate the TPS1H100 on the layout file. Could you highlight the part on the layout?

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    Genius 3280 points

    Hi Yichi,

    The yellow color box is the location of TPS1H100AQPWPRQ1, and please check a new attached layout file below. Also, they are considering to use the GND network(No.1) or external free-wheeling circuitry(No.2). Could you recommend that which one is better?

    One more thing, What do you think about the root cause of this burnt issue? Do you have any idea?

    PCB layout_yeloow color box.pdf

    Regards,

  • 0 in reply to Jeffrey Chung1
    TI__Genius 16390 points

    Hi Jeffrey,

    The layout looks good generally. One thing is the copper covering the thermal pad could be larger in for example top layer. 

    As for the No.1 and 2 options, correct me if I'm wrong, but those are serving different purposes. For option 1, it's to prevent any reverse current in events such as short-to-battery. For option 2, it's for inductive load discharge. Depending on the application situation, customer can have either one or both of them.

    As for the burnt issue, could you give me more details? Did the FET burnt itself under certain situation? Normally the FET should protect itself in over-temp event by shutting itself down. However, in repetitive inductive load discharge situation, the thermal protection wouldn't work and may burn itself without the free-wheeling circuitry added. We can investigate a little more if you can provide more background to the issue.

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    Genius 3280 points

    Hi Yichi,

    Thanks for your review and comment.

    I think that you confused between option 1(free wheeling diode) and option 2(GND network). Please check it again.

    According to customer's comment, this burnt issue had been happened on in-line process of automotive OEM like attached burnt image, but there was no issue on test and in-line process of customer. So they guess that it seems to happen when reverse polarity happens on their board like figure 42 Reverse protection with GND network of datasheet. What do you think about it?

    Schematic of TPS1H100AQPWPRQ1_2nd.pdf

    Regards,

  • +1 in reply to Jeffrey Chung1
    TI__Genius 16390 points

    Hi Jeffrey,

    Could you elaborate on the two options? I still can't see how the freewheeling diode is helping in blocking the reverse current.

    Yes the reverse current when the FET is off can burn the device since the current will flow through the body diode and cause a lot of heating on the part. Also the part can't protect itself in this case. If the customer can confirm the reverse polarity happened in their case, then the ground network should help.

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    Genius 3280 points

    Hi Yichi,

    According to the datasheet of this device, I understood that the free wheeling diode is used to discharge the inductive load, and GND network is used to protect the reverse current. Is it correct or not?

    And this comment helps them find a correct solution for this burnt issue.

    Regards,

  • 0 in reply to Jeffrey Chung1
    TI__Genius 16390 points

    Yes, your understanding is correct.

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    Genius 3280 points

    Hi Yichi,

    Thanks for your kind response. I will post it if my customer have an additional question about this issue after that.

    Regards,