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TPS61087: TPS61087 SW shorted to GND when high power output

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Replies: 10

Views: 495

Part Number: TPS61087

Hi,

Recently, I designed a boost circuit which is 5V input, 11.7V/600mA output which using TPS61087.

During testing, the output voltage, SW voltage and the L current is beautiful at 100mA/300mA/600mA output. But when the load goes up to 700mA, the IC broken. SW shorted to Ground. I changed the diode from  BA260A to SL22 which can increase the output power. The output current can achieve to 740mA. But when the load goes high to 750mA, IC broken.

I also tested TPS61087 demo, when the output current 750mA, the IC broken too. Before broken, peak inductor current hasn't catch the MOSFET current limit.

Could you please help me check what the root cause of the broken? Thanks.

  • Hi Martin,

    Did you catch the waveform of the inductor current?  And did you catch the SW voltage spike during test especially at the 600mA-700mA condition? if the Vin is ≥5V, it should be OK for the 5Vin/11.7V 700mA output. 

    Best Regards,
    Helen

    Boost DC/DC Solution

  • In reply to Helen chen:

    Hi Helen,

    I also think it should be OK, but the IC broken. I also tested the SW voltage, no over voltage spike. Thanks.

    Could you please test the TPS61087 demo also? I test the board twice, the same broken phenomenon as my circuit. Thanks.
  • In reply to Martin Wen82:

    Hi Martin,

    What is the input voltage? did you test the input voltage at the TPS61087's input cap?  Is it 5V or much lower than 5V?

    Best Regards,
    Helen

    Boost DC/DC Solution

  • In reply to Helen chen:

    Hi Helen,

    From DC Source. 5V stable, OCP set to 5A. Thanks.

    Could you please try to test the demo also. Maybe you can also meet the same problem. Thanks.
  • In reply to Martin Wen82:

    Hi Martin,

    The on board test is OK. It is OK to output 12V/800mA at Vin=5V condition. Note: this 5V is on board voltage, not the power supply output voltage.

    Best Regards,
    Helen

    Boost DC/DC Solution

  • In reply to Helen chen:

    Hi Helen,

    Thanks for the testing and suggestions.
    Could you please increase the output current to check what will happen when the board shut down? Thanks.
  • In reply to Martin Wen82:

    Hi Helen,

    I guess the parasitic inductance between the SW and the drain of MOS. And the parasitic inductance between the source of MOS and Ground cause negative voltage spike break the IC. Also, the value of schottky's parasitic cap also a factor. Thanks.

    Regards,
    Martin Wen
  • In reply to Martin Wen82:

    Hi Martin,

    During my test, when Vin=5V, Vo=11.7V, Iomax=1.1A.when Io>1.1A, the output voltage begin drop, it enters into the current limit mode.

    Best Regards,
    Helen

    Boost DC/DC Solution

  • In reply to Helen chen:

    Hi Helen,

    I test two boards again and find the final reason.

    The DC power supply was set to 2A max output current. When the TPS61087 input current hit the power supply output current. DC power supply restart and has output over shot which higher than 6V. And then TPS61087 is broken.

    Thanks for helping.

    Martin Wen.
  • In reply to Martin Wen82:

    Hi Martin,

    Thanks for the update. So this post can be closed!

    Best Regards,
    Helen

    Boost DC/DC Solution

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