DRV8432 Problems

John,

" I am using a 10k ohm resistor between GND and AGND (as per the EVK board schematic). "

This should be a 1ohm....basically a low resistance short.  

One question:  I'm using the Arduino to send a PWM signal because it's very easy to setup and use.  The PWM cycles at 500 Hz.  Could that be causing a problem?

John,

That is also a problem as the bootstrap capacitor will deplete and an UVP on the bootstrap circuit will kick in.  Need to try and keep it about 10kHz.  

Thanks for the quick response Ryan.  I've replaced with a 1hm resistor between AGND and GND.  

As far as the PWM frequency, would that cause the driver to be stuck at 0.6V?  I am going to pursue a way to get a pwm signal at that rate, but the current setup is exhibiting the following behavior:

- At startup, with no signal from the microcontroller, the controller shows an output of 0.6 V.

- When PWM goes to 100% duty cycle the controller shows an output of 0.6 V.  

- When the PWM goes to 0% duty cycle, the controller shows an output of 0.6V as well.

Thanks again for your help!

Just to confirm, the alert lines (FAULT and OTW) go high (3.3v) when everything is normal, correct?  

Thanks!

Also to confirm: for ease of prototyping, I'm using 50V capacitors all around.  Would that pose a problem (I'm running at a voltage of around 14 volts, so it should be within tolerances of the voltage I'm using).

So I've tried the setup again, modelling off the EVK boards, careful to use the same values.  I have a 12V regulator giving 11.9 volts steadily.  I put a new chip in place on the board in case I had somehow fried earlier versions.

My PVDD_X voltage is 13V.  The OUT_X voltage is 0.656 for the OUT_X now, with no PWM signal.  Both FAULT and OTW are high (3.3V).  Any idea what could be wrong?

Does this indicate anything?  Have I just wired up the chip wrong?  

John,

Please post your email address and I will see if I can get you some working hardware.

Ryan,

thanks.!

Hi John! I also tried to use this device in a circuit. I used the high current version (DKD package), but i have problems with the mechanical drawings on one of the last pages in the datasheet. 

The heat slug is placed on the bottom of the device? It's on the top side!

I used the evaluation board user guide to route my PCB and if I now check the pin 1 marking on the chip and the PCB there is something wrong.

Which version is now the correct one? 

Is the pin 1 marking wrong, or is the EVAL board PCB wrong?

Regards,

Gerald 

Gerald,

Which drawing are you referring to that is not correct?  The DKD (R-PDSO-G36) drawing in the back of the datasheet shows an arrow pointing to the Heat Slug on the top of the package.  For the DDW drawings, the thermal pad is on the bottom - DRV8412. 

Pin 1 marking is on the top as indicated in the drawing. 

Please make sure to download the latest datasheet from ti.com as I know there was an problem with this drawing at one point.  You might have an old version of the datasheet you are referencing.

Ryan,

           In  a reply to an e-mail to TI support, I was advised to use this forum. I have been designing step motor drives for about 12 years, so my questions specifically relate to the use of the DRV8432. I need to control motor current, first to match the motor rating over the range 2A to 5A, but then when operational, to reduce from 'Run' to 'Hold' current while the motor is stopped.

Is normal current control effected entirely by the PWM signals? If so what is the current to duty cycle formula?

I am using the data sheet Fig 13 schematic and values. PVDD will be 24V or 48V, GVDD 12V. M1 and M2 high, M3 low, OCC resistor 47K.

I will finish the PCB layout this week. Production is targeted for early next year.

Hi John,

If you are trying to control the current, you will need some type of current sensing (ADC, programmable comparator, etc) and additional code in the microcontroller to perform the task. Without this, the current can go to zero and then build in the opposite direction.

Can you provide more details on your current needs? We have several devices that will regulate the current at each step using simple STEP/DIR commands. For 24V operation, the DRV8818 has a built in indexer, and can handle 2.5A per winding.

We also have the DRV8711 which allows the user to configure the FETs based on needs.  

Hi Rick,

            I assume that the PWM-A and PWM-C duty cycles are Sine and Cosine modulated to effect the equivalent of microstep motion though each set of four fullsteps, and that duty cycle is converted to current in the DRV8432. Is this so? If not how is PWM used to effect stepmotor motion?

John

Hi John,

The PWM-x signals simply turn the outputs on and off. The signals do nothing to regulate current in a Sine and Cosine fashion. With a microcontroller, the PWM_x inputs can be used to control a stepper. The user can program the number of steps, the type of decay, the on and off times.

To regulate current using the DRV8432 requires adding shunt resistors in the GND_x path, a method to detect when the current has been reached, and a microcontroller to monitor the current and adjust the PWM_x signals to regulate the current.

Hi Mohit,

Can you provide more details? What are you trying to do, and what problem are you experiencing?

For reference, the DRV8412-C2-KIT is available in the estore. All documentation and code is also available through controlSUITE.

Thanks.