L6474: Can only see pulses on one of the phases?

[dvelasco]

Posted on July 15, 2015 at 22:01

A colleague and I noticed something unusual when we were using an L6474 to drive a stepper motor.

When the motor was stationary, we observed pulses on both of the motor phases.  This presumably corresponds to the PWM pattern used to generate the holding torque.  When the motor was in motion though, we only observed pulses on one of the phases.  This doesn't seem right, so what might be going on?I ask because we are trying to diagnose this unusual issue in which the motors stall at a lower speed than what we would expect.

[Enrico Poli]

Posted on July 22, 2015 at 16:55

Hi,

If the motor was in motion it is quite strange no pulses are present in one of the phases. If the current in one of the phases is not controlled the motor should immediately stall or at least have a jerky motion. Do you have some waveform to share? Enrico

[stcom9173]

Posted on June 10, 2016 at 14:30

Hi,

it seems I am observing the same phenomenon. I've attached some scope pictures. It shows the outputs on an L6470PD though. I am using the L6472PD too, which performs as specified with the same setup. So I tend to think, that there are faulty chips in the wild. It would be great if you could confirm that the behavior you observed is at least similar. ________________ Attachments : OUT1A_minus_OUT2A-running.png : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Hz8W&d=%2Fa%2F0X0000000bJI%2F0a5nzqF6wBF5IlsG82GaKhfH2Vygi1oJfA_Mm2PLFYQ&asPdf=falseOUT1A_minus_OUT2A-stopped.png : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzHw&d=%2Fa%2F0X0000000bJG%2FBWU9PxqO2GiM3NdHgk2PJhpekC3MH6Nl6h3FuEohY4A&asPdf=falseOUT1A-running.png : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzHr&d=%2Fa%2F0X0000000bJH%2Fkjqjp6hgQ_f3EFddLQjNRZdqIkR91tSlh0StEJSdowA&asPdf=falseOUT1A-stopped.png : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzHm&d=%2Fa%2F0X0000000bJD%2F564g9tIBV8qy4d9mOnzG795jDL9KWVaKS_2EaXaO9kc&asPdf=false