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DRV8320: I would like to connect 3 Hall sensor outputs to the device directly ( INLA , INHB, INLB ) and Send PWM signal from ATMEGA328P to INHA. Will this work?

MounishPatel Seetha
Intellectual 795 points
Part Number: DRV8320
Other Parts Discussed in Thread: DRV832X

1.To set DRV832x device to 1xPWM mode, I see that Mode= Hi-Z? Its quite confusing can you please explain me , how to do that?

2. I would like to connect 3 Hall sensors to the device directly ( INLA , INHB, INLB ) and Send PWM signal from ATMEGA328P to INHA. Will this work?

3. What is logic high voltage here?

Sorry for asking noob questions.. Thanks in advance, Please help 

  • 0
    TI__Guru 65220 points

    Mounish,

    1. To set these pins Hi-Z, simply leave the pin floating.
    2. Yes this is correct.
    3. Please check the recommended operating conditions table (section 7.3) in the datasheet, either 5V logic or 3.3V logic is appropriate.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Intellectual 795 points

    Adam,

    I kindly request you to clarify following doubts


    1. Can I use key2 as power lock ( when this switch is pressed power to nshdown pin and indirectly power to enable pin is also cut)?
    2. How the speed of motor is controlled? ( by controlling duty cycle of PWM applied?) ( can I use ATMEGA directly?)
    3. What happens when we change applied PWM frequency?

    4. is 100% duty cycle of PWM ...5V? so that half bridge uses maximum VM?

    5.. I got Idrive= 470mA for rise time and idrive= 1.56A for fall time. So can I use 2000mA idrive mode. will MOSFET damage if this value is more?
    6. I would like to use vds_ocp of 0.6v , is it ok to leave vds pin floating as given in datasheet
    7. Is there any resistor or capacitor that i can delete in this schematic? ( like Rshdwn , Renable, Rdir )

    Please comment if there is any mistake in my circuit. I will be very happy to correct them

  • 0 in reply to MounishPatel Seetha
    TI__Guru 65220 points

    Mounish,

    1. Yes this approach should work fine.
    2. The speed of the motor is directly tied to the input PWM duty cycle.
    3. You can change the PWM frequency but the percentage of duty cycle will still control the motor speed.
    4. Yes.
    5. The maximum recommended IDRIVE for these FETs is recommended as 235mA so I would use one of the three lowest settings for IDRIVE. Please see our IDRIVE FAQ here: https://e2e.ti.com/support/motor-drivers/f/38/t/796378
      The QGD of your FETs is 47nC and we recommend 200nS or slower for the rise/fall time.
    6. Yes.
    7. You can remove RDIR, it does not need a resistor. For nSHDN and Renable, I recommend keeping the resistors.

    The rest of the schematic looks good but please let us know when you have a layout for review because it is highly important.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Intellectual 795 points

    Adam,

    As you have said, if i use idrive lessthan 235mA, Idrive should be 120mA. but as you have recommended  in the above link. Mosfet rise and fall time should be 100ns to 300ns. If i use 120mA Mosfet rise and fall time will be much slower right? around 400ns. Is this sufficient to drive a bldc motor?

  • 0 in reply to MounishPatel Seetha
    TI__Guru 65220 points

    Mounish,

    100-200ns is the shortest time we recommend, often customers use 500ns or slower depending on their needs. For a PCB to support 100-200ns effectively the board needs to be very well designed with thick gate/source traces that are as short as possible.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Intellectual 795 points

    Adam,

    Thankyou so much for all your inputs and patience. One final question

    1. I am bit confused with thermal pad design. as recommed just adding couple of vias tied to ground is sufficient?

    2.  In the layout recommendations, I saw that  traces from GHX should be atleased 20mil wide, but i cannot go beyond 10mil. please comment on my design

  • 0 in reply to MounishPatel Seetha
    TI__Guru 65220 points

    Mounish,

    If you are using only 100-200mA of gate drive current then 10 mils should be sufficient as long as SHx traces are also 10 mils minimum.

    I cannot see the fine details of the PCB but at a basic level it looks fine.

    Regards,

    -Adam