Hi Guys!
I have problem with a Stepper Motor 24 DC drived by Motor Driver (A3950 Allegro).
At the outputs of Motor Driver i found the same value of OUT A, OUT B (24 Vdc) and a signal on NFAULT pin indicate a problem with the chip.
When I connect the motor, OUT A and OUT B (that were at 24 Vdc) fall at 0Vdc and the motor, of course, does't start.
I know that the correct values are OUT A = 24 Vdc and OUT B = 0 Vdc to rotate the shaft clockwise, otherwise OUT A = 0 Vdc an OUT B= 24 Vdc for the anticlockwise.
I have controlled all values of all pins and the values of capacitances and resistor used, but I can't understand because it doesn't work.
Thank you in advance.

 

Learn all about stepper motors at
http://www.cs.uiowa.edu/~jones/step/index.html

 

You mean DC motor control... That circuit isn't for a stepper!!

 

Learn all about stepper motors at
http://www.cs.uiowa.edu/~jones/step/index.html

Good link! But i have problem with the Allegro's driver A3950 because OUTA and OUTB result both Vbb (supply used 24Vdc), instead of OUTA=Vbb and OUTB=0.
I set: Phase=high, Enable=high (for now, in other moment i will transmitt a PWM signal), Mode=don't care(but i have setted it to high), Sleep=high. In this way i should have gotten a Forward rotation of motor's shaft.
NFAULT is low, because find a short condition, but i don't understand where is the problem.
Thank you!

 

You mean DC motor control... That circuit isn't for a stepper!!

DC Motor, sorry.

 

Is the thermal pad connected to ground? As far as I can see this chip has several Nfault conditions... Thermal overload is one..

 

Is the thermal pad connected to ground? As far as I can see this chip has several Nfault conditions... Thermal overload is one..

It does not look like this IC is intended to have a PWM input signal nor is it intended to drive a stepper motor. THUS all is fault and the different parts don't match at all. The IC manufacturer's data sheet should give some useful application information.

 

Yes! It's connected to ground. I have controlled it.
About thermal overload, i don't think so because the circuit configuration is the same indicate on the component datasheet.
What could be other reasons?

 

It does not look like this IC is intended to have a PWM input signal nor is it intended to drive a stepper motor. THUS all is fault and the different parts don't match at all. The IC manufacturer's data sheet should give some useful application information.

Sorry. I'm wrong to digit, i drive a DC motor. The PWM input signal is ENABLE, PHASE for direction of motor and MODE for decay mode. I respect the value of control logic table. I fixed all this parameters in which way only try to start the DC motor, but nothing.

 

I tried to put in short condition GND pin with one of OUTA or OUTB, the motor starts. But it is very strange...

 

The datasheet shows PWM control via the enable pin.. Pin 8 should be 24v same as the motor...

If you short out any of the out pins, you can damage the IC.. If the high side is active you'll blow it up..

 

The datasheet shows PWM control via the enable pin.. Pin 8 should be 24v same as the motor...

If you short out any of the out pins, you can damage the IC.. If the high side is active you'll blow it up..

Exactly correct, Ian. The destruction is almost certain.

 

The datasheet shows PWM control via the enable pin.. Pin 8 should be 24v same as the motor...
If you short out any of the out pins, you can damage the IC.. If the high side is active you'll blow it up..

Exactly correct, Ian. The destruction is almost certain.

I know it well. But in this case seems no damage chip, infact IC continue to be the same behavior.
I repeat, very strange...

 

Your circuit in post 1 is obviously not the circuit you are working with... For starters VPWM is connected to pin 8 ( VBB)

Can you post the exact circuit you are using..

 

This is the exact circuit. VPWM is only a name and no correspond to PWM signal. How you can look on the right picture, VPWM is supply voltage (24 Vdc).

 

News: I have 4 copy of this board and the fourth seems function correctly. Now I must understand where is the problem on the other three board.
Thank you for help me.
See you soon guys