DRV3255-Q1: BLDC motor control

Dhruv,

62V DHCP is fine if this voltage is well controlled. Do you know the max supply voltage and max transient supply voltage? We need to make sure that the supply is normally <75V with transient rating up to 90V for short periods.

Regards,

-Adam

Hello Adam,

I am giving supply to the 3 phase inverter through a battery management system which is rated at 62V and has several protection features so the over voltage or voltage transient doesn't seem to be any issue for me. I am only concerned with the DRV3255-Q1 to operate with my motor control inverter board as I have always used half bridge Gate driver for each phase. Due to better performance and protection features included in DRV gate drivers I think it may be possible to reduce overall protection circuits as well the space for each half bridge driver and peripherals which in conclusion can help me reduce my board size as well as perform better than half bridge gate driver IC. But still there is confusion whether to consider these IC or not, please suggest better.

Dhruv,

Does your project need functional safety? is it automotive? What is your ambient temperature range during normal operation?

Regards,

-Adam

Adam,

Yes, my application for motor control is for electric vehicle two wheeler to be precise. And in terms of safety I need shoot through fault protection, OV, OC, UV etc. as protection features. With all conditions to drive along with heat sinks it will be probably between 40-60 degree centigrade. 

Dhruv,

"shoot through fault protection, OV, OC, UV etc. as protection features" We have non functional safety devices which support these protection features, let me ask the team for a recommendation for you.

Regards,

-Adam 

Sure thing Adam, let's make this more interesting!

Dhruv,

Let me check with the team and I will get back to you Monday.

Regards,

-Adam

Adam,

Any updates?

Dhruv,

DRV835x would be a good device for you. If you need current shunt amplifiers for low side FET phase current feedback, DRV8353 has three CSAs. There are hardware controlled devices and SPI based variants. Take a look here: https://www.ti.com/product/DRV8353

Regards,

-Adam

Adam,

Great suggestion, This driver is quite compatible but still I want at least 3A sink source current to drive the mosfet and does it support sinusoidal 180 degree mode of operation and/or Field oriented Control?

Dhruv,

These drivers do not include commutation or control, you will need to implement the algorithm needed on your MCU of choice.

Could you explain the need for 3A gate drive, this is quite large.

Regards,

-Adam

Adam, 

Commutation algorithm is implemented from MCU. According to the MOSFET parameters from datasheet, we have calculated the sink and source current of FET with Qg, Ton and Toff time of MOSFET. Is it possible for us to set up a meeting at your convenience so that we can discuss more on this topics regarding DRV gate drivers?

Dhruv,

Please take a look at the following materials to help you decide how much gate current is needed:

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1238968/faq-how-to-determine-which-mosfets-a-gate-driver-can-support

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/796378/faq-selecting-the-best-idrive-setting-and-why-this-is-essential

Regards,

-Adam

Adam,

This documents were helpful and according to that my Qgd is 50 nC, Tr is 15ns and Tf is 48 nC which makes the source current to be 3.33A and the sink current 1.04A. Also we have thought about using CSD19536KCS 100 V N-Channel MOSFET from TI for which Qgd is 17nC, Tr is 8 ns and Tf is 5 ns. Hence, source current calculated is 2.125A and sink current is 3.4A.

Dhruv,

I think your rise and fall time targets are too low, usually we see customers using higher values. Can you comment why you need single digits of nano seconds rise and fall time?

The device has a SHX slew rate max limit of 1V/ns, this means you cannot slew 0V to 62V in less than 62ns without violating this spec.

Regards,

-Adam

Adam,

 We need high switching frequency for Electric Two wheeler of around 20KHz for 40A continuous current and less rise and fall time allows to switch mosfet faster and also deadband requirements are fulfilled.