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DRV 8307 GATE Current capacity

Dinesh Jinjala
Prodigy 60 points
Other Parts Discussed in Thread: DRV8307, DRV8308, CSD88537ND

I found that in the data sheet of DRV8307, It is written that 'DRV8307 is a three half- bridge pre-driver that drives six N-type MOSFETs 30 mA with a single power supply.' While in this linked  page(http://www.ti.com/product/drv8307/description), it is written that DRV8307 has 300mA GATE  DRIVE current for six MOSFETS. So I am quite confused for the value of the GATE DRIVE Current. I wish  this problem will be solved as soon as possible.  If i am doing any mistake then kindly inform me.  Thanks.

I have done this complaint at the error reporting page (). 

I get good reply also and thanks for reply and reply is given below:

Dear Dinesh,

 Thanks for pointing out this error.  The DRV8307 has a gate drive current of 30 mA, and the website has the error.

 If you’re using large MOSFETs for a high current motor, and need more gate drive current, the DRV8308 allows up to 130 mA but requires SPI configuration.

 For any other questions, I recommend using the E2E forum at https://e2e.ti.com/support/applications/motor_drivers/f/38

 Best regards,

 Ross

But after this reply, I get one more confusion. You said “If you’re using large MOSFETs for a high current motor, and need more gate drive current, the DRV8308 allows up to 130 mA but requires SPI configuration.”

Till now my understanding says that gate drive current is depended on gate charge of MOSFET and the switching Frequency (Normally PWM). So if MOSFET have high gate charge or if I want to switch MOFET at higher frequency then I required more gate current.

So for lower gate charge like 14nC and switching frequency 50kHz( For CSD88537ND N-Channel NexFET), required gate current is given by:

Igate= Qg * N(Number of MOSFET) * Fswitching

 

So for my example, GATE current is 4.2mA (Qg=14nC, N=6, Fs= 50kHz).

I also found out that this required gate current is depend on the GATE resistance because it controls charging time of the gate capacitance of MOSFET.

Now my confusion is ‘Which type of MOSFET can be called Large MOSFET for high current motor?’

MOSFET which have high output drain current capacity like (60A or 100A), Is this type of MOSFET can be called as ‘LARGE MOSFET’?

Is my understanding of required GATE current for MOSFET is right or wrong?

Kindly please tell me and correct my understanding.

Thank you.

  • 0
    Prodigy 60 points

    I found that in the data sheet of DRV8307, It is written that 'DRV8307 is a three half- bridge pre-driver that drives six N-type MOSFETs 30 mA with a single power supply.' While in this linked  page(http://www.ti.com/product/drv8307/description), it is written that DRV8307 has 300mA GATE  DRIVE current for six MOSFETS. So I am quite confused for the value of the GATE DRIVE Current. I wish  this problem will be solved as soon as possible.  If i am doing any mistake then kindly inform me.  Thanks.

    I have done this complaint at the error reporting page (

    Texas Instruments

    www.go-dsp.com
    Please use the form below to provide feedback on documentation. This form is not for support of any kind. If you are seeking support or have a question please use one of the links below:

    ). 

    I get good reply also and thanks for reply and reply is given below:

    Dear Dinesh,

     Thanks for pointing out this error.  The DRV8307 has a gate drive current of 30 mA, and the website has the error.

     If you’re using large MOSFETs for a high current motor, and need more gate drive current, the DRV8308 allows up to 130 mA but requires SPI configuration.

     For any other questions, I recommend using the E2E forum at https://e2e.ti.com/support/applications/motor_drivers/f/38

     Best regards,

     Ross

    But after this reply, I get one more confusion. You said “If you’re using large MOSFETs for a high current motor, and need more gate drive current, the DRV8308 allows up to 130 mA but requires SPI configuration.”

    Till now my understanding says that gate drive current is depended on gate charge of MOSFET and the switching Frequency (Normally PWM). So if MOSFET have high gate charge or if I want to switch MOFET at higher frequency then I required more gate current.

    So for lower gate charge like 14nC and switching frequency 50kHz( For CSD88537ND N-Channel NexFET), required gate current is given by:

    Igate= Qg * N(Number of MOSFET) * Fswitching

     

    So for my example, GATE current is 4.2mA (Qg=14nC, N=6, Fs= 50kHz).

    I also found out that this required gate current is depend on the GATE resistance because it controls charging time of the gate capacitance of MOSFET.

    Now my confusion is ‘Which type of MOSFET can be called Large MOSFET for high current motor?’

    MOSFET which have high output drain current capacity like (60A or 100A), Is this type of MOSFET can be called as ‘LARGE MOSFET’?

    Is my understanding of required GATE current for MOSFET is right or wrong?

    Kindly please tell me and correct my understanding.

    Thank you.

  • 0 in reply to Dinesh Jinjala
    TI__Guru** 114905 points

    Hi Dinesh,

    Have you seen this application report, Understanding IDRIVE and TDRIVE in TI Motor Gate Drivers ?

    This should answer many of your questions.

  • 0 in reply to Rick Duncan
    Prodigy 60 points
    Yes sir, I have seen that.

    Sir can you tell me what type of FILTER and COMPENSATOR is used in DRV8308? I have try to find out center frequency and the phase at center frequency. I have try to calculate it by using frequency domain analysis.

    can you tell me out what is Integrator Frequency in DRV8308 register INTCLK? what is the use of that clock?
    I didn't find any information about INTCLK in datasheet and other user manual also.

    Thanks for reply.
  • 0 in reply to Dinesh Jinjala
    TI__Guru** 114905 points
    Hi Dinesh,

    I have contacted our expert on this device. He is currently out of the office. His response may be delayed.

    Please feel free to ping us again early next week if you have not heard from him.
  • 0 in reply to Rick Duncan
    Prodigy 60 points

    Thanks. I will wait for him for solution.

  • 0 in reply to Dinesh Jinjala
    TI__Expert 4650 points
    Hi Dinesh,

    Sorry for the delay.

    The filter and compensator in the DRV8308 are both designed to compensate for the two-pole open loop response of the motor. Without the filters included in the feedback circuit, the driver will measure the motor speed as being 180 degrees out of phase which will result in incorrect commutation.

    INTCLK is the integrator clock frequency. The digital integrator inside of the DRV8308 shifts in an error term to the integrator clock on each INTCLK cycle. A faster INTCLK clock will result in more samples being shifted into the integrator.
  • 0 in reply to Phil Beard
    Prodigy 60 points

    Can you tell me how Fclk and Filter and Compensator pole-zero frequency are related?

  • 0 in reply to Phil Beard
    Prodigy 60 points

    I have used 0.7 Nm torque motor and I required very high torque. Is it possible with any best Filter and Compensator configuration? I have seen DRV8308 datasheet and In application note I find that they have used very low torque motor(0.120 Nm). I want to use this BLDC Driver in high torque industrial application. 

    Please give reply as soon as possible.

    Thank you.