• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 30 subscribers
  • Views 1789 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Connect 2 Half Bridge Drifers between DRV8701 and the 4 N-Mosfets

user4315872
Prodigy 150 points
Other Parts Discussed in Thread: DRV8701, LM5109B, DRV8711, TIDA-00872

dear ladies and gentlemen,

for my DC Motor I need a higher Supply Voltage than the DRV8701 withstand.
The N-Fet output stage needs more Current for Charge than the DRV8701 can deliver.

Is it possible to connect 2 Half Bridge Driver e.g. LM5109B between the DRV8701 and the 4 N-MOSFETs?

The DRV8701 should only control the ON/OFF sequence of the FETs and the LM5109B should drive the

N-FETs with the right Current and Voltage.

Could I disable the charge pump of the DRV8701, so that the Output of Low-Side has the same Voltage Level than the High Side?

Thanks in advance

Thomas Straßer

  • 0
    TI__Guru** 114905 points

    Hi Thomas,

    It may be possible to do so. It would require some additional circuitry between the DRV8701 and LM5109B to workaround overcurrent and predriver faults, and to lower the voltage at the inputs of the LM5109B.

    In addition, dead time may have to be adjusted for the additional circuitry.

    The charge pump cannot be disabled, as the VCP is monitored and will disable the outputs.

    A starting point for ideas is TIDA-00872. This uses the DRV8711 which has similar output structures and had to workaround several of the same restrictions.

  • 0 in reply to Rick Duncan
    Prodigy 150 points

    Hi Rick,

    thank you for your proposition.
    for my DC motor application I need the high-side FET power stage too.
    On the attachment is a schematic with my solution proposal.

    It should able to drive DC Motors up to 100V and large Current.

    kind regards

    Thomas

    TI_DC_Motor_Controller.pdf

  • 0 in reply to user4315872
    TI__Guru** 114905 points
    Hi Thomas,

    A few comments:
    1) Please tie the IDRIVE input directly to AVDD. This disables the high side OCP monitor.
    2) SH should be connected to complete the high side FET control circuit. It is recommended to connect a voltage divider of two resistors in series from GHx to GND.
    3) The current from the GHx pin should be 500uA or less. The voltage should drop ~10V from GHx to SHx across the first resistor. This first voltage drop should be connected to SHx.
    4)The GLx resistor divider may not be required. Max voltage is 10.5V, so it is your choice.
    5)The mcu may have to PWM the inputs to prevent the depleting the bootstrap cap.
  • 0 in reply to Rick Duncan
    Prodigy 150 points
    Hi Rick,

    thank you forapproval of my proposed schematic.
    I have some Questions about Your reccomendations.

    VDD is approximately 24VDC in my planned circuit.

    2) SH should be connected to complete the high side FET control circuit.
    Whre should I connect SH?

    5)The mcu may have to PWM the inputs to prevent the depleting the bootstrap cap.
    Which Inputs did You mean?
    Which bootstrap cap did You mean? Is it part of the charge pump?


    kind regards
    Thomas
  • 0 in reply to user4315872
    TI__Guru** 114905 points
    Hi Thomas,

    According to the LM5109B datasheet, 24V violates the absolute maximum of 18V. If possible, VDD = 12V would be preferred.
    Assuming VDD = 12V, the GHx will be 12 + 10.5 or 22.5V max.

    2) SH should be connected to complete the high side FET control circuit.
    Whre should I connect SH?

    It is recommended to create a voltage divider from GHx to GND using a minimum of 45kOhms (GHx/500uA). The mid point of the divider should be approximately 10V below GHx. This midpoint should connect to SHx, and can also connect to the HI input of the LM5109B.

    5)The mcu may have to PWM the inputs to prevent the depleting the bootstrap cap.
    Which Inputs did You mean?
    Which bootstrap cap did You mean? Is it part of the charge pump?

    Please refer to the simplified schematic of the LM5109B. You will see the resistor, diode, and bootstrap cap used to fully enhance the high side FET.