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DRV8411: Current rating question verses DRV8833

Jason Whitehead
Prodigy 20 points
Part Number: DRV8411
Other Parts Discussed in Thread: DRV8833,

The DRV8411 data states that it is a 4 Amp driver, which is quite a bit more than the DRV8833 which is rated as 1.5A RMS or 2A peak; however, both the FET resistance and the thermal resistance of the DRV8411 part appear to be higher than those of the DRV8833... normally this would mean that the DRV8411 would be able to drive less current. I was wondering if there was more information on this.

  • 0
    TI__Mastermind 37683 points

    Hi Jason,

    The 4A is just the max peak current for a short duration of time. Both the devices are designed with different max current peak transient limits. Since the peak current duration is not that long, thermal dissipation is not really a big concern. The type of current that matter for thermal purposes is the RMS or continuous average current. In this situation, variables like ambient temperature, FET RDSon, thermal resistance values, heat sinking on PCB, etc, will affect the thermal performance of the IC.

    Regards,

    Pablo Armet

  • 0 in reply to Pablo Armet
    Prodigy 20 points

    Hi Pablo,

    Thank you for your response. There doesn't appear to be an RMS current value on the datasheet for for the DRV4811 which is making it difficult to compare the parts. Since posting the original question I have found there is a full scale current of 2.1A noted on this page https://www.ti.com/product/DRV8411 verses 1.5A on https://www.ti.com/product/DRV8833 - although I am not sure if this is equivalent to RMS, the 1.5A does match the RMS value given for the DRV8833. Unless there are some more details available on how the parts have been characterised, it may be something we just need to test.

    Regards,

    Jason.

  • 0 in reply to Jason Whitehead
    TI__Mastermind 37683 points

    Hi Jason,

    The reason the RMS value is not specified in the datasheet is because there are many factors involved in the calculation, some of which are beyond the control of the IC design. 

    This training video provides useful information for calculating power dissipation in motor drivers. 

    Regards,

    Pablo Armet