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Original question:

TIDA-00643: TIDA-00643

TIDA-00643: LAUNCHXL-F28027 C2000 Piccolo MCU F28027 LaunchPad

Anushka Agarwala
Prodigy 130 points
Part Number: TIDA-00643
Other Parts Discussed in Thread: DRV8305, TMS320F28027

Hi,

In reference to TIDA-00643, I am trying a design a system which can run a Brushless DC Motor with higher power.

Test Procedure :

For testing, I tried running my motor at different values of USER_MOTOR_MAX_CURRENT from 5 A to 23 A. Using a Watt-Meter I measured the current draw which was found to be pretty accurate at peaks. 

Observations :

1. It runs smoothly from 0-15 A.

2. It jitters from 15-23 A. 

3.It throws a fault when run at values greater than 23 A.

Goal : I want to increase USER_MOTOR_MAX_CURRENT  

I have three assumptions :

1. Is it any component's (i.e. DRV8305, shunt resistors, MOSFETs ) maximum rating that is limiting the USER_MOTOR_MAX_CURRENT ?

2. Is it the layout of the board that is limiting it?

2. Is it any parameter in the firmware that is limiting it?

3. Is it the thermal protection circuit in the DRV8305 that is shutting it off ?

Thanks,

Anushka

  • 0
    TI__Guru** 109690 points

    1. All three factors have an impact on the maximum current.

    2. Yes, especially long-time running with a load.

    3. USER_MOTOR_MAX_CURRENT in user.h

    4. No, but will turn off the MOSFET if the Vdson is greater than limitation value. 

    Btw, you may take a look at the datasheet of DRV8305, you should find more information about your question 1&4.

  • 0 in reply to Yanming Luo
    Prodigy 130 points

    Hello,

    Thanks for your response. I changed the shunt resistance to a lower value to allow around 38 A and I changed the following parameters to compensate for the change to allow 30 A :

    1. user_motor_max_current

    2. iq_full_scale_current 

    3. adc_full_scale_current

    My board is still not able to pull more than 15 A. Could the gate driver or the microcontroller unit be limiting it? As per your suggestion, I looked at the DRV8305 and TMS320F28027 but I could not find the maximum working current for any of them. Please help me out.

    Thanks,

    Anushka

  • 0 in reply to Anushka Agarwala
    TI__Guru** 109690 points

    You should change the Vds by setting the registers of DRV8305, please take a look at the datasheet of DRV8305.