Questions about BQ2057T

Intellectual 2095 points

Kevin Wen

Replies: 2

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Hi team,

My customer Harbin Fenghua is evaluating our BQ2057T, they copy the design on datasheet Page.10 figure4 and only difference is they use a different MOSFET SI3457 instead of SI6475. But during the test, they found that MOSFET heat up very quickly, would you please have a look this issue and show your suggestion? If more inforation is needed or need to do some test, please let me know.

Thanks.

Kevin

• BQ2057T

Intellectual 2095 points

Kevin Wen

• Jul 2, 2015 3:47 PM
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2 Replies

• Expert 7720 points

  

  Wenjia Liu

  

  • Jul 2, 2015 5:11 PM

  Kevin,
  
  Please refer to the formula (7) on page#15 of the datasheet to calculate the power dissipation over the MOSFET. And then you can refer to the DISSIPATION RATING TABLE on page#5 to calculate the expected temperature increase. It could be true that during the beginning stage of charging the power dissipation is big and then generate a lot of heat.
  
  Thanks,
  Wenjia

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• Mastermind 46790 points

  

  Wang5577

  

  • Jul 6, 2015 4:03 PM

  bq2057 is a linear charger. The FET power dissipation is (Vin-Vout) x Iout. It shouldn't be related the FET. Do they test the thremal performance on a same board? Are they both soldered good?

  Best Regards,

  Wang Li

  Motor Drive Solutions

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