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BQ24650: MOSFET damaged for 24VDC

Pranay Upadhyay
Prodigy 40 points
Part Number: BQ24650
Other Parts Discussed in Thread: BQ25756E

Tool/software:

BQ24650-Based Battery Charging Circuit
We have designed a new PCB for a solar-powered battery charging system using the BQ24650 IC as the core charge controller. The design follows the TI datasheet recommendations closely, including the use of suggested passive and active components. Notably, we used the SI7288DP N-channel MOSFET as the system power FET.

Observed Issue
The circuit operates successfully at 12V input with no apparent failures.

However, when the input is increased to 24V, the SI7288DP MOSFET gets damaged during operation.

Design Overview
The input voltage range specified for the BQ24650 is up to 28V absolute max, with recommended operation up to 26V.

SI7288DP was chosen due to its low Rds(on) and adequate current handling.

Gate drive circuitry, power dissipation, and switching behavior were designed in accordance with application notes and layout recommendations.

  • 0
    TI__Mastermind 31306 points

    Hello Pranay,

    Can you provide more details?

    Which MOSFET was damaged Q1 or Q2 or both?

    Can you provide your schematic?

    What is battery voltage?

    What is charge current?

    How long after charging did the FET get damaged? Do you have a way to monitor Temp of MOSFET?

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 40 points

    Dear Christian, 

    Which MOSFET was damaged Q1 or Q2 or both? - Q1 and Q2 are in single package Both were getting damaged 

    What is battery voltage? - It is working on 12V and getting damaged on 24V

    How long after charging did the FET get damaged? - Suddenly after power On

    Solar_Panel_Project_2.0_04-02 (2).pdf

  • 0 in reply to Pranay Upadhyay
    TI__Mastermind 31306 points

    Hello Pranay,

    Pranay Upadhyay said:
    What is battery voltage? - It is working on 12V and getting damaged on 24V
    Pranay Upadhyay said:

    Observed Issue
    The circuit operates successfully at 12V input with no apparent failures.

    However, when the input is increased to 24V, the SI7288DP MOSFET gets damaged during operation.

    I'm confused, is the input 24V, or is the battery voltage 24? This is a buck charger, the input has to be higher than the battery voltage.

    Your resistor divder indicate the max charge voltage is 25.2V

    What is battery charge current?

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 40 points

    Dear Christian, 

    We are trying to use this design to charge 24V Battery using 24V solar panel. 

    For this application, first we are giving 24VDC input from external power supply and observing output.

    We are getting 12VDC output when giving input from 12VDC using external power supply but MOSFET damaged when connecting input  24VDC  using external power supply. 

    Now, we have not tested and considered for charge current. 

  • 0 in reply to Pranay Upadhyay
    TI__Mastermind 31306 points

    Hello Praynay,

    This is a Buck-Only charger, the input has to be higher than battery voltage:

    Do you see this issue if you use a higher input voltage?  You're trying to operate at 100% duty cycle, which could lead to the damaged of these MOSFETS.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 40 points

    Dear Christian,

    Thanks for your valuable input. 

    So I think we can not use this part for 24VDC. 

    Please let me know suitable part for 24VDC battery charging. 

    Regards, 

    Pranay

  • 0 in reply to Pranay Upadhyay
    TI__Mastermind 31306 points

    Hello Pranay,

    Pranay Upadhyay said:

    So I think we can not use this part for 24VDC. 

    Please let me know suitable part for 24VDC battery charging. 

    This part is suitable for 24V battery charging, however it is a buck-only charger. The input has to be higher than battery voltage. This is why I suggest testing at higher input voltage.

    Pranay Upadhyay said:
    Please let me know suitable part for 24VDC battery charging. 

    Another option is BQ25756E, which is a buck-boost charger, and should be suitable for your requirements.

    Best Regards,

    Christian.