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LAUNCHXL-F28379D: Setting the base current and base voltage using BOOSTXL-DRV8305EVM

Javier Cartagena
Prodigy 10 points
Part Number: LAUNCHXL-F28379D
Other Parts Discussed in Thread: BOOSTXL-DRV8305EVM, C2000WARE, BOOSTXL-3PHGANINV

I am trying to adapt the Dual Axis Servo example (C:\ti\c2000\C2000Ware_MotorControl_SDK_4_02_00_00\solutions\boostxl_3phganinv) to a single BOOSTXL-DRV8305EVM. I am able to get the proper PWM signals on an o-scope but as soon I set motorVars[0].ctrlState to run, I get an overcurrent fault. I can't seem to get past BUILDLEVEL1 and see the pulses and ramp generator on the graph. I suspect my base current (M1_BASE_CURRENT) and scaling factor (M1_MAXIMUM_SCALE_CURRENT) are off. The BOOSTXL-DRV8305EVM passes the shunt voltage to a differential op-amp with a gain of 10 and an offset of 1.65V. The shunt is 7 milliohms and the reference voltage is 3.0V taken from the launch pad. What would be the proper way of setting these values?

Here is my attempt:

I set M1_MAXIMUM_SCALE_CURRENT = [Vref / (Gain*Rshunt)] - Offset = [3.0 / (10.0*0.007)] - [1.65 / (10.0*0.007)]. And I've set M1_BASE_CURRENT to half of this value.

Any insight would be greatly appreciated!

  • 0
    TI__Mastermind 38295 points

    Hi,

    Have you already taken voltage sensing differences of the hardware into account? i.e. M1_MAXIMUM_SCALE_VOLATGE

    The BOOSTXL-3PHGANINV uses in-line current sensing while the BOOSTXL-DRV8305EVM uses low-side current sensing. There may be other differences that need to be made in SW to accommodate this change as well (like when the ADC sampling occurs).

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Mastermind 38295 points

    Hi,

    I back calculated based on the 3PHGANINV hardware. It seems you need to multiply your M1_MAXIMUM_SCALE_CURRENT calculation by 2x, same for your M1_BASE_CURRENT.

    M1_MAXIMUM_SCALE_CURRENT = 2* {[Vref / (Gain*Rshunt)] - Offset} = 2*{[3.0 / (10.0*0.007)] - [1.65 / (10.0*0.007)]} = 38.57

    M1_BASE_CURRENT = M1_MAXIMUM_SCALE_CURRENT / 2

    Best,

    Kevin