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DRV8833 PWM control

Rajvel Murugesan1
Prodigy 90 points
Other Parts Discussed in Thread: DRV8833, DRV8811, DRV8824

Hi,

I am using DRV8833 IC for my application.I plan to use this IC for my satellite application .I am going to operate at the voltage of 8V.The  current should flows through the load(Inductance) in one direction approximately 22.5 sec and current direction should be reversed in another direction approximately 22.5 sec.Will this IC suitable for the above application..?

Also I need some of the information I need for this part number

1. What is the maximum VDS voltage of the internal FETs.

2. Max Freq of operation if 50Khz which is  indicated in datasheet, but what is the maximum duty (On Time) allowed ?
3. What is the charge pump output voltage.

4. The chip has an internal  OCP, will you able to program the OCP deglitch time ?

Kindly clarify the above questions

Regards

Rajvel M

  • 0
    TI__Guru** 114905 points

    Hi Rajvel,

    Please see answers below.

    1. maximum Vds is the same as the absolute rating of VM 11.8V. at ON state, Vds is monitored by the OCP function.

    2. 50kHz means the internal PWM frequency when current regulation level tripped. The effective inputs frequency is only limited by input deglitch time(450ns) and propagation delay time(1.1us). Usually if external PWM is used, about <=20kHz external PWM control will be fine. So about 1.5/50us=3% minimum duty can be used. But maybe we never need such low duty for motor control.

    3. Charge pump voltage is not fixed and related to VM voltage. You can test VCP and get by Vvcp - Vvm at your VM condition. it should be 4~7V at VM from 4~10V

    4. the internal OCP deglitch time is not programmable.

  • 0 in reply to Rick Duncan
    Prodigy 90 points

    Dear Rick,

    Thanks for the information.Regarding the Question number 2 I have asked what is the maximum duty cycle I can operate..? that means suppose If i am going to operate in 20KHz as my total time then what is the maximum ON time I can give (shall I operate in 90% duty cycle..?

    Is the maximum external frequency is limited only to 20KHz...?That means I cannot operate more than 20KHz as external frequency..?

    Regards

    Rajvel M

  • 0 in reply to Rajvel Murugesan1
    Prodigy 90 points

    Dear Rick,

    I need some other information also.

    Here is my Exact requirement

    supply Voltage---8.2V

    Current Required---50mA

    Load :inductance coil of approx 25mH

    Continuously current in one direction upto 22.5sec and then again 22.5 sec current direction should be reversed.I need to use H bridge circuit.

    will the selected part number suitable for the above application..?

  • 0 in reply to Rajvel Murugesan1
    TI__Guru** 114905 points

    Hi Rajvel,

    The DRV8833 is suitable for your application.

    The answer to the maximum duty cycle depends on how the device is configured.

    If the device has a 4 Ohm sense resistor in the xISEN path to use the internal chopping circuit, the current chopping circuit will take precedence and set the maximum duty cycle. Once the current level of 50mA has been reached, the DRV8833 will transition into slow decay mode and PWM at 50kHz. This may not be the desired operation.

    If a 0 Ohm resistor is used in the xISEN path to ground, the duty cycle is now controlled directly by the xIN1 and xIN2 pins. In this case the maximum duty cycle can be 100%, assuming that the overcurrent circuit does not trip.

  • 0 in reply to Rick Duncan
    Prodigy 90 points

    Thank you for your help.I need some of the basic doubt also.can you clarify the same..?

    The device(DRV8833) is capable of working 2.7 to 10.8V.

    I am using 8.2V as my supply voltage.this voltage may come from solar panel or Battery voltage(which is available in the Satellite).Normally we will choose the device which is capable of supporting double the times the required voltage for deration(8.2V means atleast it should support 16.4V or more since it is a critical requirement in the satellite.).Is there any chance there to develop higher voltage across the load when switching my load current from one direction to another direction(fortunately i have no idea in this )..?

    will this device support for momentary sudden increase in voltage..?

    If the device is not support means Is there any other part number is there to support my requirement..?

    Kindly help in this regards

    regards

    Rajvel M

  • 0 in reply to Rajvel Murugesan1
    TI__Guru** 114905 points

    Hi Rajvel,

    If the voltage increase exceeds the absolute maximum of 11.8V, the device may be damaged.

    What is the minimum and maximum VM voltage for this application? If the minimum voltage will always be above 8V and the motor is,devices like the DRV8811 or DRV8824 may be a better fit. Thes has a recommended maximum VM above 35V.

    If the minimum voltage will be less than 8V, most devices working at this level have a absolute maximum of approximately 12V. There is a possibility that the voltage can exceed the absolute maximum. Steps must be taken to avoid this. Usually the voltage can increase when the motor is stopped suddenly.

    In these cases, there are several circuits that are typically used to minimize the voltage increase. Increasing the capacitance on VM can help. Also if you don't need to reverse the motor suddenly, slowly stopping the motor helps.

    There is a list of devices available at http://www.ti.com/lsds/ti/amplifiers-linear/integrated-motor-driver-products.page