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BQ76940: when Charging Q1 N-MOSFET increase temperature.

Expert 2440 points

Replies: 5

Views: 115

Part Number: BQ76940

Dear Sir,

When charging BAT PACK. Q1  N-MOSFETs are increase Temperature and very hot.

When TURN OFF Q1  N-MOSFETs. GATE voltage is 4V. 

When TURN ON Q1  N-MOSFETs. GATE voltage is 12V.

If BAT CHARGING Voltage and BAT PACK are same. When TURN OFF Q1  N-MOSFETs. GATE voltage is 0V.

BAT CHARGING Voltage : 84V

BAT PACK voltage : 70V

could you let me know advise me about this issue.,

please refer below wave form.

3250.LOW-SIDE FET_gate voltage abnormal.pptx

  • Hi Dexter,

    Can you let me know which FET part number you are using and your typical charge and discharge currents? Are the FETs properly rated for the voltage applied and is the RDSon reasonably low?

    Best regards,

    Matt

    Please click "This resolved my issue" button if this post answers your question

     TI provides design resources and design advice (including technical, schematic, code and/or system review) “as is” and with all faults.  All information in this or related correspondence is provided subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).

  • In reply to Matt Sunna:

    Hi Matt.

    I'm SONGUO H/W engineer.

    I attach test data.200403_SONGUO_FET-1.pptx

    We are using the FET below.(IPB048N15N5LF)

    Charge/Discharge is up to 20A~100A.(20s/72V) and the FET is controlled by UCC27424.

    [Additional question]

    1) Is it safe to use a resistance value of R301(1M --> 150kohm)?

    2) What are the benefits of using a p-ch FET for UCC27424?

    Please check the attachment.

  • In reply to HYOUNG RAE RYU:

    Hi Dexter,

    I am not an expert on the UCC27424, so I am reassigning your question to the expert for this device.

    Best regards,

    Matt

    Please click "This resolved my issue" button if this post answers your question

     TI provides design resources and design advice (including technical, schematic, code and/or system review) “as is” and with all faults.  All information in this or related correspondence is provided subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml).

  • In reply to Matt Sunna:

    Hi Dexter, 

    I have sent you an email, let's continue to debug there while I mark this thread as resolved.

    Regards,

    -Mamadou

  • In reply to Mamadou Diallo:

    Hi Mamadou,

    I got the your email. 

    Thank you for your support!!

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