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DRV8301/2 GVDD external drive.

Other Parts Discussed in Thread: DRV8301, LM5109

Hi, 

I might exceed the 30mA RMS current for GVDD on my project. I think I saw somewhere that you can drive GVDD externally with say 12V to disable the internal regulator and provide the current externally. Is this correct?

(at 30mA and 40-50V Vin-Vout difference the internal regulator will produce 1.2-1.5W of heat, which is also something to take into account....)

  • Hi Roger,

    I believe you are referring to this POST

    As stated in the post, it is not recommended to drive the GVDD externally.

  • Nope. Had not read that. :-) 

    So... With 30kHz PWM switching requirements, the DRV8301 will never be suitable to drive more than 300nC worth of mosfets. 
    I've been considering "splitting" all the functions of the DRV into multiple special purpose chips for this project, but if the 300nC is a hard limit, that becomes a requirement. It also lifts the "60V limit" that the DRV imposes.

    The current requirements in this project are such that multiple parallel mosfets is very likely necessary. The rumor was: "The DRV is already struggling to drive the 300nC MOSFETs", and this turns out to be the 30mA limit on GVDD. But placing 2 or 3 of those mosfets in parallel then is impossible if it is not possible to externally drive GVDD.

  • Roger,

    You are correct. There is a limitation in the size of the external MOSFET DRV8301 can drive. 300nC is an extremely large amount of gate charge.

    What kind of application are you looking at?

    What do you mean by lift the 60V limit?

  • We do not recommend supplying GVDD externally because the internal circuitry has been designed with only the internal 30mA GVDD supply in mind.
  • We need 10kW, preferably 12kW of output power. Staying below 60V, means for me +/-50V as a practical limit. This also means we won't have "dangerous DC voltages" inside our system. Then we're looking at around 200-240A. 

    The mosfets I was looking at are the IRFS3006 (I've played with them around 10 years ago) or their slightly more modern brothers. IRFS3006: 300nC, Alternative: IRFS3107: 240nC. IRFS3206, irfs7534: 300nC. auirls3036: 160nC. The 3036 sounds like a better plan then. The DRV might then be able to drive two in parallel. 

    We're looking at FOC to avoid torque ripple. If the PWM frequency drops to just a few per 1/6th of an electrical revolution, then I expect to get torque ripple again. Correct? We need 25k eRPM. 

    With "lift the limit" I mean that if we can't use the DRV8301 (or '02) we won't be bound by the 60V limit of the DRV. A separate FET driver like the LM5109, a separate buck converter for 12V and 3.3V supplies, and separate opamps for the current amplification will allow us to rethink the "dangerous DC voltages" issue, and possibly go to "90V, 110A": Lower currents, less copper in the supply wires etc. All nice things. The demo-kit we have already has "2 current amps" in the DRV and a separate opamp for the third. This means we get to test the "separate opamp"... :-) 

  • Hi Roger,

    Sounds like the LM5109 is a better fit for your application. The DRV8301 is a highly integrated solution intended to remove and integrate alot of the things you described, but cannot quite achieve the power you are looking for. It was initially designed for < 6kW applications (60V/100A). We will take information this into consideration for our future developments though.

    Out of curiosity, can you share the actual application?