L6472 parameters setting

[sctisz]

Posted on October 29, 2014 at 15:54

Hi,

I'm new to L6472 here, and from reading its datasheet, I think it would be a perfect fit to my application which will need to drive a NEMA34 motor to go relative high speed (such as 12 rotations per sec.).  I've been reading AN4158 which is related to L6472 and am puzzled by some of the concepts there, could someone help explain? thanks! Sam *) The concept of target switching time (it sets the target PWM frequency of the control system) is not clear to me,?what's the relationship between this parameter and the step speed (or step period)? (or is there any relationship between these two parameters?) And why it's better to have a fixed PWM frequency? is this PWM frequency the same PWM that creates the microstepped phase currents in microstep mode? *) it seems to make auto adjusted decay and predictive current control work, 6 parameters need to be set properly: TOFF_MIN, TON_MIN, TOFF, TOFF_FAST, FAST_STEP, TSW. It was not clear to me how these six variables shall be set properly, is there any concete example of the analytical steps someone should take to set values (or a value range) for these variables/parameters? #l6472

[larken]

Posted on November 06, 2014 at 03:25

The pwm switching frequency is not related to the input step pulse frequence. The PWM is controlling current in the winding. Its humming along at about 20Khz regardless if the motor is spinning or stopped.

   Its sometimes better to have a fixed PWM frequency to prevent motor ringing noise as opposed to a fixed off time that make the frequeny change depending on the current.  The Step pulse moves along a pointer to a table that specifies where on the sine/cos current table and phase the PWM should work from. Larry

[Lorenzo1]

Posted on March 09, 2015 at 11:22

I resume this old thread, because I have some issue about AN4158 content and L6472 datasheet content.

I'm studing how L6472 current control works, and I'm a little confused.With reference to L6472's datasheet...At page 40 I read that T_FAST has default value ''19h, 1us/5us'' but the table at page 45 says something different. Numerically speaking 19h is the default value, but which is the correct encoding: 1us/5us or the table at page 45? ... Is the table for T_FAST correct?With reference to AN4158...You write about Toff at page 21, but which is the register corresponding to Toff in L6472 configuration? How can I assign Toff duration?I can match all others parameters, I can find Toff_min used in ''predictive current control'' but I can't identify a Toff register used in ''auto adjusted decay''.Thanks

[Enrico Poli]

Posted on April 08, 2015 at 13:43

Hi,

The values reported in the table of page 40 are wrong. The actiual values are TOFF_FAST = 4 us, FAST_STEP = 20 us. Thanks for your feedback! We will fix this in the next datasheet release. When the predictive current control is enabled the toff is automatically adjusted in order to obtain a switching period equal to TSW. When the predictive current control is disabled the toff is constant and equal to TSW. Regards Enrico

[John Gaffke]

Posted on September 01, 2017 at 15:50

Hi,

I am in the same boat as outlined in Sam's original question. I have the L6472H Discovery board and want to drive a stepper as high as 2400step/sec. at .8Amps/phase and 42volts. 

Can someone provide (or point me to) an outline/answer to the 2nd part of Sam's questions? Specifically, how does one properly set

: TOFF_MIN, TON_MIN, TOFF, TOFF_FAST, FAST_STEP, TSW

to run the L6472 after reading 

AN4158, and if there is

any example or analytical steps someone should take to set values (or a value range) for these variables/parameters? 

Thanks,

John

[Nathan Coon]

Posted on September 11, 2017 at 23:37

I would also like to know how to do this.