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DRV8301: MOTOWARE - DRV8301 parameters

Asif Ahmed
Expert 1570 points
Part Number: DRV8301
Other Parts Discussed in Thread: MOTORWARE, , TMS320F28027F, DRV8305

Hello -

I have custom hardware running InstaSPIN-FOC using a TMS320F28027F MCU and a DRV8301 gate driver. I am using Motorware 18, lab 11a currently.

I am digging through motorware code and have a question regarding the DRV8301 current limit parameters:

I notice that Motorware (drv8301.c specifically) is setting the GATE_CURRENT parameter to 0.25A (though it is capable of 1.7A). This looks like a potential issue. What is the implication of changing this to 1.7A? I am using quite large D2PAK FETs.

Any insight is appreciated.

Best,

asifjahmed

  • 0
    TI__Guru** 114905 points

    Hi Asif,

    If you have not done so, please read the blog: e2e.ti.com/.../what-is-a-smart-gate-drive-architecture

    Increasing the gate current can help increase the PWM frequency, but there are a few possible side effects.

    First, the gate slew rate is faster which can introduce additional noise in the system.
    Second, the faster slew rates could cause unexpected coupling between the high and low side FETs.

    It is generally recommended to set the gate current based on the equation: MOSFET Slew Rate = MOSFET QGD / Gate_Current Setting. This is a slightly modified version of the equation in the DRV8305 datasheet.

    Also please be sure to meet equation 3 of the DRV8301 datasheet.

  • 0 in reply to Rick Duncan
    Expert 1570 points

    Thanks Rick.

    My FETs are quite large, with an Rds(on) typ. of 2.8mA and Qgd of 55nC. The default setting in motorware of 0.25A for gate current applies to the built-in FETs which have a much lower Qgd (9 nC).

    Based on your suggestion of using the equation Slew Rate = Qgd / Gate_Current:

    Using stock FETs on the BOOSTXL:

    9nC / 0.05A = 180 nS

    And with mine:

    55nC / 0.25A = 220 nS

    Are these correct? If so, seems like I could benefit from a slightly higher slew rate (more efficient)? But the next setting up on the DRV8301 for gate current is 0.70A, which is considerably higher, and gives:

    55nC / 0.70A = ~79nS

    Any advice is much appreciated.

    -asifjahmed

  • 0 in reply to Asif Ahmed
    TI__Guru** 114905 points
    Hi Asif,

    Your calculations are correct. Increasing the gate current to 700mA could help with efficiency, but may generate more noise.

    You will have to determine which is the best setting for your system.