DRV3255-Q1: MOSFET drive capability

Ian Wylie

Part Number: DRV3255-Q1

Hello,

we have a need to increase the PWM switching frequency of our 3-phase BLDC 48V motor driver up to >40kHz, but our current driver can only go a little above 20kHz with the MOSFETs we're using because of its limited charge pump load current spec. (the charge pump supplies the gate drivers), so we're looking for a new driver.

It needs to be 3-phase, with the usual driver and MOSFET protection features, and ISO26262 ASIL B rated.

We can't get hold of the DRV3255-Q1 data due to NDA restrictions, but can anyone tell me without violating NDAs if this device has sufficient charge pump or regulator capacity to drive 'big' MOSFETs at PWM frequencies above 40kHz?
If it can then we may try to pursue an NDA again (if TI are interested this time).

Our relevant MOSFET parameters are: Qg = 216nC max.
Assume we are using FOC so we're probably switching all 6 MOSFETs.

Thanks,
Ian

10 months ago

0 Anthony Lodi 10 months ago

TI__Mastermind 21886 points

Hi Ian,

Thank you for your question!

Yes, the DRV3255-Q1 is capable of driving 6 total FETs with 216nC each at 40kHz using FOC.

Regards,

Anthony Lodi

0 Ian Wylie 10 months ago in reply to Anthony Lodi

Prodigy 60 points

Thanks Anthony - just so I can do some thinking here is it possible to tell me either what the actual drive capability of the DRV3255-Q1 is (i.e. relevant charge pump or regulator max load current), or the max PWM frequency possible with this spec MOSFET?

Regards,
Ian

0 Anthony Lodi 10 months ago in reply to Ian Wylie

TI__Mastermind 21886 points

Hi Ian,

Given that this device is covered under NDA, I am not comfortable with providing that specific information. However, you are welcome to reach out to TI to request an NDA if you are interested in learning more specifics about the device.

Thanks for your questions!

Regards,

Anthony Lodi

0 Ian Wylie 10 months ago in reply to Anthony Lodi

Prodigy 60 points

Thanks Anthony, unfortunately we've tried "reaching out" to TI already who have said that they are too busy to talk to us, so no joy there I'm afraid.

How about just telling me the maximum PWM frequency that we might be able to drive these MOSFETs at, as I mentioned in my original post that we need to go above 40kHz.

Thanks,
Ian

0 Anthony Lodi 10 months ago in reply to Ian Wylie

TI__Mastermind 21886 points

Hi Ian,

what is the maximum PWM frequency that you intend to operate at?

Regards,

Anthony Lodi

0 Ian Wylie 10 months ago in reply to Anthony Lodi

Prodigy 60 points

Hi Anthony - we don't yet know, we're exploring what we can do so there's no requirements except "how high".

thanks,
Ian

0 Anthony Lodi 10 months ago in reply to Ian Wylie

TI__Mastermind 21886 points

Hi Ian,

Maybe some things to think about while deciding what is the PWM frequency that you want to operate at:

1. The higher the PWM frequency operation, the more MOSFET switching losses are present.

2. Usually the PWM frequency will be determined by what is the maximum amount of current ripple that is allowed for your design. The current ripple will be dependent on the inductance of the motor and the PWM switching frequency. From this information you can calculate your target PWM frequency.

Regards,

Anthony Lodi

0 Ian Wylie 10 months ago in reply to Anthony Lodi

Prodigy 60 points

Thanks Anthony - we're well aware of these and other factors, but if you aren't able to tell me what the DRV3255 max. frequency with these MOSFETs is then let's just call this one closed.

BR,
Ian

0 Anthony Lodi 10 months ago in reply to Ian Wylie

TI__Mastermind 21886 points

Hi Ian,

Unfortunately I am unable to provide more information publicly without an NDA, so we will have to leave this one here.

Regards,

Anthony Lodi

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DRV3255-Q1: MOSFET drive capability