DRV8343-Q1: The Idrive setting facor with MOSFET

A.W

Part Number: DRV8343-Q1

I'm a little confused about the Idrive setting. Below is what the spec for DRV8343S says.

For MOSFETs with a known gate-to-drain charge Qgd, desired rise time (tr), and a desired fall time (tf). IDRIVEP >Qgd * tr

However,It seems that the MOS will charge Qgs first than Qgd. Is the VGS rise time possible to concern the Qgs+Qgs, not just Qgd?

Btw, for Qg restriction:
Trapezoidal 120° Commutation: IVCP > Qg × ƒPWM
Sinusoidal 180° Commutation: IVCP > 3 × Qg × ƒPWM

Is it a slip of pen?It can be multiplied by 2?

Trapezoidal 120° Commutation: IVCP > 2 × Qg × ƒPWM ( for 2 MOS turn on the same time)
Sinusoidal 180° Commutation: IVCP > 6 × Qg × ƒPWM (for 6 MOS turn on one duty cycle)

and the Qg is for Gate charge total？

Regards

Arrow

over 3 years ago

+1 Matt Hein over 3 years ago

TI__Mastermind 21805 points

Hi Arrow,

Thanks for your question!

If I understand you correctly, you are asking why we use IDRIVEP > Qgd * tr to calculate the rise time. When we talk about rise time, we mean the rise time of SHx, or the output to the motor. We are not talking about the rise time of the MOSFET gate. This rise time is the time that the output is switching from low to high. Since the MOSFET VDS changes during the Miller region (Qgd), we can use that component to calculate the approximate rise time of the motor output. You can read more about this in our app note Understanding Smart Gate Drive.

Your second question seems to be related to the current capability of the charge pump (IVCP). In the DRV8343-Q1 there is a charge pump (VCP) which supplies power for the high-side MOSFETs and a separate low-side regulator (VGLS) which generates the voltage for the low-side gates. Since the charge pump is only used to drive the high-side MOSFETs, you can ignore the low-side MOSFETs for this calculation.

Thanks,

Matt

0 A.W over 3 years ago in reply to Matt Hein

Intellectual 330 points

OK, I got it.

Thanks

Arrow

Matt Hein said:
the

0 Matt Hein over 3 years ago in reply to A.W

TI__Mastermind 21805 points

Please let me know if you have any further questions!

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DRV8343-Q1: The Idrive setting facor with MOSFET