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Icomp current of DRV401

ttd
Mastermind 9355 points

Other Parts Discussed in Thread: DRV401

Dear Technical Support Team

Absolute max of Icomps shows "Icomp SHort Cicuit +250mA" and note(4 ) shows "Power-limited; observe maximum junction temperature."

Does it means that When junction temperature is inside of Tj spec(from -40 to 125 degree),

can Icomp flow any current(there is no regulation on the current value) ?

Best Regards,

ttd

  • 0
    Guru 140200 points
    Hi Ttd,

    datasheet says:

    "The two outputs ICOMP1 and ICOMP2 are linear outputs.
    Therefore, the power dissipation on each output is
    proportional to the current multiplied by the internal voltage
    drop on the active transistor. For ICOMP1 and ICOMP2, this
    internal voltage drop is the voltage drop to VDD2 or GND,
    according to the current-conducting side of the output.

    Output short-circuits are particularly critical for the driver
    because the full supply voltage can be seen across the
    conducting transistor, and the current is not limited by
    anything other than the current density limitation of the
    FET. Permanent damage to the device can occur.

    The DRV401 does not include temperature protection or
    thermal shut-down."

    This means, that there's no protection and that the chip is in danger to overheat.

    ICOMP OUTPUT SWING TO RAILvs OUTPUT CURRENT curve on page 9 of datasheet shows that an internal voltage drop of about 250mV occurs when the output current is 250mA. This gives a heat dissipation of 62.5mW. This is what the chip can easily handle. But if this current flows during a short circuit event, the heat dissipation will be 1.25W and this can overheat the chip, depending on cooling situation.

    So, if you cannot prevent the output from becoming short-circuited then limit the output current to 250mA. And how long the chip will withstand this short circuit depends on junction temperature, or by other words the cooling situation. So, brief short circuits might be allowed, provided that the output current is limited to 250mA.

    Kai
  • 0
    TI__Mastermind 34860 points

    Hello ttd,

    Yes you need to observe the power consumed by the device during this short circuit.  Please also be aware you will limit your current below the 250mA if your compensation coil resistance is large.  For example with a 5V supply and a 30Ω load (compensation coil) the max current I would expect is 166.6mA for the compensation coil. 

    For design considerations please consider you can reach the rails on the ICOMP pins but normally that will not be the case.  As we have a minimum of 4.2V with a 20 Ω load.  Most of the power from the part will be used for higher current measurements as it needs to drive the compensation coil but please keep in mind the part needs current as well for the field probe and other parts of the internal circuit.