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Full bridge PWM controller gate driver

Pritesh Metha
Prodigy 190 points
Part Number: DRV8701
Other Parts Discussed in Thread: DRV8702-Q1, DRV8703-Q1, CSD18510Q5B, CSD18540Q5B

Hi,

We are designing 60 Ampere 24V brushed DC motor driver.For prototyping we used DRV8701E and it was working but we are using 3 parallel mosfet in each arm/each side of Mosfet H bridge(total 12 mosfet in H bridge).But when we added one extra mosfet to each arm/side of H bridge(4 parallel mosfet) it glows error LED because IDRIVE current of DRV8701 is only 150mA peack .

So can you please suggest any Other Full bridge PWM controller gate driver which having more IDRIVE capacity in High and Low side.

  • 0
    TI__Guru** 114905 points

    Hi Pritesh,

    The DRV8702-Q1 and DRV8703-Q1 are possible alternatives. The IDRIVE is higher at 240mA vs the 8701 at 150mA.

  • 0 in reply to Rick Duncan
    Prodigy 190 points

    Hi,

    Can you please tell me ,it is work with 4 parallel mosfet in each side of h bridge. Mosfet is CSD18510q5b.

    According to following application note,DRV8701 could also work but practically it is not working.

    Application Note: http://www.ti.com/lit/slva714

  • 0
    Prodigy 190 points

    Part Number: DRV8701

    Hi,

    We are designing DC brushed Motor driver.

    Driver rating- 45V 80A(Continuous) 32khz.

    Mosfet: CSD18540q5b

    We have already developed one prototype board using above parts and rating. We are connecting 4 Parallel mosfet in each side of h bridge.Total 16 mosfet.

    It will glows error led while driving 4 parallel mosfet but if we removed  one mosfet from each side it is working with 3 parallel mosfet.

    1) We have used following formula from SLVA714C application report-

    IAVG = QG × # MOSFETs Switching × Switching Frequency

    IAvg = 41nC * 8 mosfets * 32Khz     =10.49mA                    (8 mosfet in highside and 8 mosfet in low side of h bridge)

    Required gate drive current is less than 150mA but still it glows error.

    2) In DRV8701 datasheet,Page no. 29,External fet selection field-  

    The DRV8701 FET support is based on the charge pump capacity and output PWM frequency.

    Qg<(Ivcp/fpwm)<12mA/32khz<375nC

    for 8 mosfet approximate Qg=8 * 41nC =328nC

    So in both 1 and 2 cases our calculations are within limit but still it is not working with 4 parallel mosfet and work with 3 parallel mosfet.

  • 0 in reply to Pritesh Metha
    TI__Guru** 114905 points

    Hi Pritesh,

    Do you know why the nFAULT signal is asserting?

    Please review the fault response table (Table 7) in the datasheet to determine possible causes.

    The recovery provides information on the type of fault.

    Can you provide a schematic? This may assist in determining what is happening.

  • 0 in reply to Rick Duncan
    Prodigy 190 points

    Hi,

    I am attaching Schematic.

    Can you please tell approximate pick and average gate driving current required to drive single  CSD18510q5b.

    1185.ti forum.PDF

  • 0 in reply to Pritesh Metha
    TI__Guru** 114905 points

    Hi Pritesh,

    Thank you for the schematic. The schematic shows there are no series gate resistors to the parallel FET.

    When using parallel FETs, a series gate resistor should be place between the GH/GL output and gate of each FET. The series resistors (2 to 5 Ohms) are intended to avoid ringing. An internet search for paralleling FETs explains the reasons.

    We still need to determine why the nFAULT is asserting. It is difficult to fix the problem without knowing if the fault is a PDF or OCP.

    Would you please provide scope captures of GH/GL/VDS to determine the cause of the fault after adding the resistors.