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DRV8343-Q1: The function for the capacitor between low side MOS D and GND in DRV8343S-Q1EVM

Part Number: DRV8343-Q1
Other Parts Discussed in Thread: DRV8343S-Q1EVM, BOOSTXL-DRV8320RS, CSD18543Q3A

Hi

I found that there are  capacitors used between  each low sidE MOSFET' Drain and GND in DRV8343S-Q1EVM,whose Designators are C47/C48/C49 with value of 10nF(sch in MD005A).

However this is not used in BOOSTXL-DRV8320RS board.

Is it necessary for the use of drv8343s? or is it used for decrease the SHX voltage spike?

If this is needed, which value should it be set?

The 10nf capacitor is desgined for the specific MOSFET(CSD18543Q3A) or just a  empirical value?

Regards

Arrow

  • In section 8.3.5.8,it shows this is for OLA detection.

    Will this capacitor effects the normal switching for BLDC, since this capacitor is right between D/S of low side MOS?

    Regards

    Arrow

  • Hi Arrow, 

    The BOOSTXL board was made later than the other two boards that you mentioned. The C2000 team did not optimize this board for general DRV8320RS evaluation, but moreso for sensorless control. So it:

    1. Lacks the phase output capacitors included on the DRV8343 EVM
    2. Borrows the power stage implementation of the previous BOOSTXL-DRV832x EVMs

    The capacitors C47-C49 are used to decrease any transients on the SHx/DLx nodes, dampen ringing or oscillations on the switch node, and are optional in design.

    If needed, then we recommend a small capacitance value of around 10 nF according to the EVM design. More capacitance will reduce the SHx transient but increase the settling time on the switch node if ringing is present; less capacitance will reduce the settling time but increase the possible transient at the SHx node. You can use trial and error to determine how much capacitance may or may not be needed, depending on the application requirements.

    Best,

    Johnny

  • Hi Arrow,

    Is there any further assistance that you need here?

    Thanks,

    Matt

  • Hi Arrow,

    I'm going to close this thread for now. If you have further questions please click the "Ask a related question" button!

    Thanks,

    Matt