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Original question:

Heat sink size selection for the DRV8432

DRV8412: heat sink for DRV8412 or DRV8432

Pere Casanovas
Prodigy 20 points
Part Number: DRV8412

I'm running a motor control with DRV8412 and it is running at up to 6A and is getting hot. Could yu recomend a heatsink for DRV8412 or if not possible beacause the slug is at bottom, Do you recommend to change the design to a DRV8432. Anyway what heatsink do you recomend for working at 6A ?

  • 0
    TI__Guru 56650 points

    Pere,

    I cannot give a direct answer what heatsink should meet your requirement because we don't have thermal test data with different heatsinks and don't know your target temperature and ambient temperature.

    First, please check how "hot" is the DRV8412 on your board comparing with your maximum allowed temperature rising target.

    If there is not a big gap between your target temperature and current board temperature, please make sure a good thermal connection underneath the DRV8412. The datasheet layout example section gives the recommendation. Also, a previous e2e post talked about this thermal pad connection https://e2e.ti.com/support/archive/internal/int-motor_drivers/f/40/p/71308/258853?tisearch=e2e-sitesearch&keymatch=DRV8412%20heatsink#258853

    If the IC temperature is still "hot" with a good thermal pad layout, we may change to DRV8432 with a heatsink. After you know your target temperature, you can estimate the system required RθJA = (Ttarget-Tambient)/Pdiss  (Pdiss is the IC power dissipation at 6A load). The heat sink resistance equation is given in datasheet "Thermal Considerations" section: " RθJA = RθJC + thermal grease resistance + heat sink resistance." We need to pick a heatsink to meet that RθJA requirement. For example: visit https://www.digikey.com/products/en/fans-thermal-management/thermal-heat-sinks/219 and check "Thermal Resistance" column and find a right size/shape heatsink.

    If you want to keep using what you have and add a thermal heatsink on the DRV8412 solution. You can try two heatsinks on the bottom (opposite of DRV8412 layer) of the board and check the temperature changes.  And then, calculate out your board thermal resistance and pick a heatsink to meet your requirement.

    With heatsink1 RθJA_heatsink1= DeltaT1 / Pdiss.  (Temperature rising DeltaTx can be measured, Pdiss is the IC power dissipation at 6A).

    With heatsink2 RθJA_heatsink2= DeltaT2 / Pdiss

    So, we get RθJA_heatsink1/RθJA_heatsink2 = DeltaT1/DeltaT2 (1)

    RθJA_heatsink1 = RθJ_board + heat sink resistance1 (2) 

    RθJA_heatsink2 = RθJ_board + heat sink resistance2 (3) 

    Heat sink resistance1 or 2 can be found from the heatsink spec (like the previous digikey link lists). According to (1), (2) and (3), we can estimate RθJ_board. And then, we can pick a heat sink to meet your target temperature. Luckily you may find a right heatsink during heatsink 1 or heatsink 2 test. BTW, these calculations are based on good thermal contact between the heatsink and the thermal pad or bottom layer thermal ground copper.