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.

DRV8701: DRV8701 with parallel mosfet

Part Number: DRV8701
Other Parts Discussed in Thread: CSD18510Q5B

Hi,

I am using DRV8701E as gate driver to drive for CSD18510Q5B mosfet.

4 parallel mosfet in each arm of H bridge.So total 16 mosfet in H bridge.

I drive current source is set to 150mA and sink 300mA.

When there is 4 parallel mosfet in each arm of H -bridge then it raise fault indication but in 3 parallel mosfet it works finne.

Calculation- CSD18510Q5B 

Qgd= 21nc.,

Isource= 150mA.

T(slew)= Qgd/Isource=(8*21nc)/150mA=1.12 uSec     //For 8 mosfet slew time,4 on high side and 4 lower side

Average Current : IAVG = QG × # MOSFETs Switching × Switching Frequency

                              = 21 nc * 8 * 4Khz= 672 uA

All parameters are in range, still with 4 parallel mosfet it raises fault condition and works fine with 3 parallel mosfet. 

  • Hi Pritesh,

    Have you determined the type of fault by referring to Table 7 of the datasheet?

    Do you have series gate resistors to each FET? A web search for "parallel MOSFETs individual gate resistors" wil find articles explaining the need.

    Is it possible the FETs are not disabled when trying to enable the opposite FETs? If this is occurring, the DRV8701P may be a better choice, allow the insertion of dead time. The DRV8701P will require more resources to switch from Forward/Reverse -> Coast -> Brake and  Brake -> Coast -> Forward/Reverse. Also there will some additional efficiency loss due to current flowing through the body diode of two FETs when in coast mode.

  • Hi Pritesh,

    Do you have any updates?

  • Pritesh,

    I am going to close this post since it doesn't have update. You can re-open by posting the update.