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DRV8432: DRV8432 thermal calculation

龙飞 黄
Prodigy 10 points

Part Number: DRV8432

hello, i have a question about the DRV8432 thermal calculation

the spec of DRV8432 shows it can output 2*7A continous and 2*12A peak.

but when i do the thermal calculation i found if i output 2*7A current, the Tj will be 311℃ which exceed a lot from the maximum Tj 150℃

below is the calculation of the thermal

  • Tj= Ta+RθjA*Pd
  • Pd=Imax^2*（Rds(on)high+ Rds(on)low）*2
  • Imax=7A
  • Rds(on)high=Rds(on)low=0.11Ω
  • RθjA=13.3℃/W
  • Ta=25℃
  • Tj=25+13.3*21.56=311℃

if we want to keep the Tj below 150℃,and use two full bridge drive two BDC motor, the maximum current should not exceed 2*4.6A, this is miss match the output current with 2*7A

could you help me to answer my confuse and give me some advise about is it possible to use this IC to output 2*6.2A continous current

thanks a lot

  • +1
    TI__Guru 54665 points

    Hello,

    The 13.3 number in the table is a little misleading..depends on the heat sink you use.  Please see section 10.3 in the datasheet for a better understanding on how to calculate theta-JA for the heat sink you are planning to use.  These numbers are usually in the low single digits like <5 and then the math will work out.  

    However, if you want to consider a lower Rdson option, please look at the DRV8245-Q1.  This is the lowest Rdson option in our portfolio and as you could use 2 separate devices, no heat sink would be required.

    https://www.ti.com/product/DRV8245-Q1

    There is also a thermal calculator at the bottom of the page.

    Regards,

    Ryan