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DRV8462: how drv8462 know relation between required torque and ATQ_CNT parameter

Daisuke Nakamichi
Prodigy 20 points
Part Number: DRV8462

Hi support team.
Regarding ATQ function, could you explain how drv8462 know relation between required torque and ATQ_CNT parameter.
According to Fig7-27 in datasheet, motor current is decide by required torque and ATQ_UL parameter.
If measured ATQ_CNT parameter is higher than ATQ_UL, drv8462 will increase motor current.
To achieve this function, I think that the relationship between the required torque and the ATQ_CNT parameter at each motor current must be known.

  • 0
    Prodigy 20 points

    However, the figure7-28 shows that the learning routine is executed in only one current setting(0.5*Amax).

  • 0 in reply to Daisuke Nakamichi
    TI__Mastermind 44525 points

    Hi Nakamichi-san,

    Learning routine executes with two current values, see below info from datasheet. Please also review this application note for more information on auto torque functionality and setup. https://www.ti.com/lit/an/slvaff1/slvaff1.pdf . 

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    Prodigy 20 points

    Dear Murugavel-san

    Thank you for your reply.
    According to the information you sent, ATQ_LRN is executed by 2 current settings.
    In my understanding, ATQ_LRN is the parameter which related with resistive loss of motor.
    I want to know how DRV8462 know the relation between ATQ_CNT and required torque(Does it also measured by ATQ_LRN learning step?).

  • +1 in reply to Daisuke Nakamichi
    TI__Mastermind 44525 points

    Hi Nakamichi-san,

    I just got back to work from my personal travel. Sorry about the delayed response. Let me cite the following snippets from the application note. After a successful learn the ATQ_LRN parameter is determined like you mentioned. This will be a fixed value as mentioned in the first snippet. ATQ_CNT component is the variable component which will vary linearly with load torque. ATQ_CNT is internally computed in the auto torque close loop system of the auto torque engine of the device. It gets the necessary information from the phase current feedback. Please also refer section "2.2 Current Control" of the application note. ATQ_LRN and ATQ_CNT are two separate parameters. After a learn ATQ_LRN is determined and will be a fixed value component. ATQ_CNT is the variable parameter determined by the closed loop feedback system and it can be tuned as desired using the loop parameter settings.

    I hope this information gives you the answers you were looking for.

    Regards, Murugavel