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Some additional phase current required on DRV8301 kit

Mojo
Expert 1570 points
Other Parts Discussed in Thread: DRV8301, CONTROLSUITE, MOTORWARE, BOOSTXL-DRV8301

Hi,

I need additional ~20A on the DRV8301 kit, i.e from 42.5 to about 60A.

I use motors of about 5-30 uH, 28VDC.

Can the power circuit handle this ?

further, for the current sense I thought of the following :

1. The full scale of the ADC for current sensing is set to 82.5A full scale, so that needs to be changed,  through the resistors around the OPAMP (whose output is EXT_Ix-FB) ?

2. Rshunt - do I need to change it ? I'm thinking in sense of the drv8301... does the drv8301 uses this shunt for internal purposes or just to output the voltage on the SO0,SO1 pins ?

3. Change OC_ADJ_SET in drv8301, according to table 9 ? I actually don't understand this because the FETs being used on the board have Rdson ranging from 0.0039 to 0.0082 (and I assume all FETs have range from Rdson). This implies that the current limit is not stable at a value and the range is huge (up to more than two times between 3.9m and 8.2m). For example, the original setting for drv8301 in the software is 0.75Vds. If we calculate the current limit - this is huge - 0.75/4m = 180A !! did I get this wrong ?

Thanks a lot

  • 0
    TI__Guru** 119340 points

    1. Yes, no issue. In fact, if you use the current sense channels that route through the DRV8301 PGAs they are already scaled to just over 60A (you can look at the controlSUITE projects) and I know a customer who changed scaling and FETs to push over 100A with this PCB.  I know of another customer who has // the FETs with DRV8301 and is driving over 300A.

    2. With the DRV8301 EVM the shunt signals we use for MotorWare projects don't go through the DRV8301 at all, they go directly to external OPA which then go to the MCU.  The shunt sets the gain of the circuit as seen by the formulas in SPRUHJ1 Chapter 5

    3. Again, with the default SW in MotorWare we arent' using the PGAs or anything on DRV8301 for our current sense. I believe it is set-up for over current. We decided to use 3 external gain circuits.  With BOOSTXL-DRV8301 we did use the on-chip PGAs and 1 external OPA for the W phase.

    you may want to ask this question on Applications --> Motor Drivers forum