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BQ24773: BQ24773_temperature rise in Inductor

Mihir Bhatt
Intellectual 290 points

Hello,

Our current requirement is 10A in which charging current of battery is 4A and system current is 6A. In this case temperature rise of various components is given below.

2. High side MOSFET : 78C 

3. Low side MOSFET : 60C   

4. Power Path FET : 65C

We have also kept inductor away from the board just to ensure that other components are not heating an inductor. But in this case also, temperature of inductor is going upto 80C. As per the inductor datasheet there will be 40C temperature rise in inductor at rated Irms which is 12A. So what would be the reason behind this temperature rise in Inductos? Please suggest possible solution.

Note: Experiment is done at ambient 25C. 

Waiting for your response. 

Regards,

Mihir

  • 0
    TI__Guru 56650 points
    "As per the inductor datasheet there will be 40C temperature rise in inductor at rated Irms which is 12A." What is the current ripple? Some inductor vendors can help you calculate the inductor loss. www.vishay.com/.../
    After you have the inductor loss estimation, you can check the inductor datasheet to see if it makes sense.
  • 0 in reply to Wang5577
    Intellectual 290 points

    Hello Wang,

    Hope you are fine. Thanks for your prompt response. 

    Given below is the configuration of charger chip:

    1. Maximum battery charging current- 4A
    2. Maximum battery Voltage- 4.2V
    3. Switching frequency-600KHz
    4. Power adapter specs: 15VDC/3A

    Average system load is 5.7A (max) , so in the scenario when both unit load and battery charging current is being drawn from the buck converter total output current requirement becomes 9.7A (approx.).

    In this scenario the maximum temperature of different parts is as given below:

    a) ACFET/RBFET (DMG4800LSD-13) : 96 ֯C 

    b) High side MOSFET (BSZ0902NSATMA1): 85 ֯C

    c) Low side MOSFET (BSZ0902NSATMA1): 94 ֯C

    d) Inductor (SRP1038A-2R2M) : 98 ֯C

    This temperature is measured when unit is working at 27 ֯C room temperature .

    It will be really helpful if you can please provide your suggestions to reduce the temperature rise.

    PCB is of 4 layers with size 50 mm x 28.5 mm and 2OZ copper thickness.

    Schematic and pcb layout files are attached for your reference.

    PCB layout.pdf

    Regards,

    Mihir.