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BQ24600: The temperature of the BQ24600 is too high.

Downey Kim
Expert 2675 points
Part Number: BQ24600

Hi TI team,

My customer did design Battery charger.

The specification is as follows:

Battery : 3Cell (13000mAh)

charging voltage : 12.6V

charging current : 2~4A

we have tested by setting 2A charge current. The temperature of the BQ24600 and high-side FET are too high. (IC surface temperature: 90~110°C)

1. There are many questions on E2E due to the temperature problem of BQ24600. Is there a BQ24600 own defect?

2. I have attached the designed circuit and PCB file. Please tell us how we can improve it.

Thanks.

0724.AMOSENSE_P_RX_Charge_Rev2.0.pdfP_RX_Rev2.0(Cad file).zipP_RX_Rev2.0_gerber.zip

  • 0
    TI__Genius 10240 points

    Hi Downey,

    The BQ24600 is a charger controller and it provides the 1.2MHz gate driver to the two FETS of the buck regulator. The heat is from the power loss of the driver circuit. The loss is proportional to the switching frequency and the gate charger of the FETs. It is not the defect of the device and any driver will have the loss. Enough copper area should be designed for the FET and charger to dissipate the heat resulting from the loss. You can also check the switching node of the charger and compare to the Figure 14 on the datasheet to make sure the FET has been driven properly with reasonable turn on and off time.

  • 0 in reply to ezhao
    Expert 2675 points

    Hi Eric,

    Thanks you for the advice. 

    I think that the switching line has been designed sufficiently thick.

    Do you think no problem with the circuit designed?

    Thanks.

  • 0 in reply to Downey Kim
    TI__Mastermind 24075 points

    Hi Downey,

    Yes it looks like PH node has been designed with enough thickness. Keep in mind that as BQ24600 has 1.2MHz switching frequency, this contributes to increased switching losses (switching losses directly proportional to switching frequency). One thing to look at would be your selection of MOSFET for Q1 and Q2. You are using NTD6414ANT4G which is a 100V 32A rated MOSFET which is overkill for 2A-4A charging application and for an input voltage (VDS of Q1) that would not exceed your input voltage. Using such a big beefy FET with high Qg (gate charge) will result in increased MOSFET driver loss: 

    MOSFET gate driver power loss contributes to the dominant losses on the controller IC when the buck converter is switching. Choosing a MOSFET with a small Qg_total largely reduces the IC power loss to avoid thermal shutdown. Refer to Eq 22 from datasheet. 

    Rest of layout looks good.