Dual MC33926 Motor Driver

Having real trouble understand product docs. D1/D2, In1/In2. Which is speed, which is direction, how you hook this thing up to MCU? Any sample pics for mcu hookups?

In1 - Logic control. Can PWM. Lower down, it says direction control. PWM direction?
D1 - Disable input? Speed control? What?

Lost. I just want to pwm left and right with 3.3v mcu. How to hookup simple case? tia

BTW - the Save button seems to bit me each time I post here. Hit save it then asks to save draft. Whoop, not what I want, go Back, and loose your post. I would make save harder to find. Submit is 99.5% of cases.


You can think of the inputs as being logically ANDed together, so you have multiple options for controlling things. When you choose one approach, you have to set the others to the “logical one” setting so that your other signals can propagate through. The two disable lines let you put PWM on them for speed control; typically, you would use one and set the other to the value to enable the output. In that scenario, you would not PWM the IN1 and IN2 lines, and you would use three total lines per motor.

As an alternative, you can just permanently deactivate the disable inputs and then PWM the IN1 and IN2 lines appropriately. In this second scenario, you need only two lines (per motor), but they both need to be PWM outputs.

Regarding the “save” option, I usually write my posts in some other editor so I don’t have to trust a web browser and the details of how some web site might handle cases like the one you described.

- Jan

“As an alternative, you can just permanently deactivate the disable inputs and then PWM the IN1 and IN2 lines appropriately. In this second scenario, you need only two lines (per motor), but they both need to be PWM outputs.”

Thanks. So I will concentrate on this scenario for now.

mcu out pwm1-> IN1
mcu out pwm2 -> IN2
D1 -> jump to gnd?
D2 -> jump to gnd?

  1. If IN1/2 is doing pwm speed. How should I control direction for each?
  2. What freq should PWM be set at?

I realize I am still off base, but light should turn on.


A large point of the two disable inputs is that they are inverted relative to each other. As it says on our pin description table: “when !D2 is low, OUT1 and OUT2 are high impedance”; thus, to let the outputs be active, you have to set the input high. The other one needs to be low. Note that those are the values we provide next to those inputs for jumpering them to override the default states.

If you make IN1 low and PMW IN2, you’ll get one direction; make IN2 low and PWM IN1, and you’ll get the other direction.

- Jan

I ended up doing a simple writeup that may help someone else here
staceyw1.wordpress.com/2011/03/0 … ez-domino/

Thanks for sharing. Does this mean it’s working for you? You don’t have the grounds connected between the boards, unless you’re using the same supply for both of them or have their grounds connected separately, which still isn’t that good of a solution.

- Jan

IIRC, this method was using two seperate 12v supplies. I tore it down to test same with your smaller controller so can’t look at.
Are you saying even with complete seperate supplies you should connect GND between boards? I think I was testing for complete issolation to see if that would work. tia

Yes, you absolutely must have ground connected between the boards. Otherwise, what do you expect any of the voltage levels to mean? You should expect current to go in through the Vdd pin; where would it come back?

The reason it worked for you is probably that you always had at least one of the control inputs low, so the current could return through there. But that’s definitely not something to count on or do on purpose.

- Jan

I see where we may not be on same page.

  1. Yes the VDD must have been connected back to MCU 12v supply. So that is error on my diagram.
  2. It sounded like you wanted MCU 12V and the motor HighV grounds connected together.

I don’t know what you’re saying in your first point. Do you understand the point that if you connect something like Vdd, you have to connect a corresponding ground? Otherwise, how would any current flow?

For the second point, my goal is not necessarily to tie your two power supply grounds together externally; I was just speculating that you might have done that (your diagram implies that; it’s not good to use two symbols with the same label (green triangles labeled “GND”) if they are not actually connected). However, since there is no electrical isolation, you will necessarily end up with a single ground node that is the reference for the whole system.

- Jan