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Problem with FB on the Dual MC33926

I have a problem with my dual driver MC33926. This driver I have connected to arduino mega to control two motors. Problem is, that both motors are running and I can control this motors, but ont he M1FB I have a 0,05V output and on the M2FB I have 0V output. I tested 3 already used drivers with the same result and yesterday I used next completly new one driver with the same result. What can be a reason ? Is possible that all drivers are broken ? Why only one channel and always M2FB ? Why the new one ? Is there any way how to check more ? Thank you for help. Alex

Hello.

How are you measuring or reading those voltages (e.g. are you using the analogRead() function or directly measuring the pins with a multimeter)? Also, can you tell me more about your setup? What motors are you using? (Linking to a datasheet or product page would help.) How are you supplying power? What kind of load is on the motors? What duty cycle are you using to command your motors? Can you also send pictures that clearly show the motors, motor driver, and the rest of your setup?

-Jon

Hi,
I have the same problem with the FB pin.
It gives me strange readings with the arduino analogRead().
My Motor runs at 8V and 0.1A and it reads 0, 3, 12, 8, 0, 1, 2, 14, 1, 0 ,…
The times between the readings are 100ms.

Those values are about what we expect for measuring that low of a current with the FB pin. The MC33926’s analog current-sense feedback is an instantaneous measurement, so it reflects the current draw at the moment you are reading it. This is one reason why there is a range of values that you are measuring over the time you are measuring it. Another reason is that the current-sense on the MC33926 is just not very accurate at sensing very low currents like what you are trying to measure.

-Jon

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Thanks that clarifies much. Add a line to your great description of the part and it will help a lot of people like me with underdimensioned motors for the driver.

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Almost two years later and some of us are still having the exact same problem. Add this little tidbit to all of the board spec sheets where you use this chip please! No-load testing is often the first thing we do with a new setup.

Hello.

Thank you for the feedback. We added something more to the current sense section of the product page.

- Ben

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