DRV8412: Brushed Motor Driver

Hey Burak,

Ibrahim Burak Keskin said:

1) I will be driving two DC motors bi-directionally. So, natural operation mode of the device is Dual Full Bridge Mode (M3=0, M2=1, M1=1). According to the datasheet, in this mode,complement of the control signal (PWM_A) of half-bridge A is fed to other half bridge B. In this case, is bi-directional operation possible? How can one apply brakes? I think this mode is only suitable for full speed (100% duty cylce) opreation. Am I correct?

There are three modes with Dual Full Bridges (Mode 1, 2, and 4).  "In mode 1 and 2, PWM_A controls half bridge A, PWM_B controls half bridge B, and so forth Figure 8 shows an
application example for full bridge mode operation."  Your question here is about mode 4.  In this case if you run the motor at greater than 50% duty cycle it will drive one direction, less than 50% the other direction.  So 0% PWM would be full speed forward, and 100% full speed reverse.  

Ibrahim Burak Keskin said:

2) I had a closer look at the first typical application (section 8.2.1). In the design parameters (Table 3.), operation mode is said to be parallel full bridge. I believe that it is not the case for this typical application. Are there any typo? Also in the schematic in the typical application all mode selection inputs (MX) are set to 0. 

Looks like it's running in Mode 1, since M1-M3 are all set to GND like you say:

Ibrahim Burak Keskin said:

3) Should I use the first operation mode (M2=0, M1=0) rather than fourth operation mode (M1=1, M2=1)? Because I believe that in this case, one has full control over H-bridge (two control signals for each H bridge). Though, I wondered if I can use the latter operation mode or not.

With mode 4 you lose granularity of control (only 0%-50% instead of 0%-100%), and the signal is complimentary like you note, but the advantage is that you only need 2 PWM outputs from your MCU instead of 4.  Mode 0 or 1 gives you more control over all, since you can control the half-bridges independently.  

This is a fairly old device (2009), you may want to consider a newer device like the DRV8251A or the upcoming DRV8962

Regards,

Jacob

Ibrahim Burak Keskin said:

I will be using DRV8412 (potentially DRV8432) to drive Brushed 24V DC motors in a bi-directiona manner..

Bidirectional: speed or position control? 

Ibrahim Burak Keskin said:

Mode (M3=0, M2=1, M1=1). According to the datasheet, in this mode,complement of the control signal (PWM_A) of half-bridge A is fed to other half bridge B. In this case, is bi-directional operation possible?

Sure this mode is ok to drive motor bidirectional. But you have half of the PWM duty cycle resolution. I think mode (000) is best for you if the MCU has 4 PWM output signals.

Ibrahim Burak Keskin said:

How can one apply brakes? I think this mode is only suitable for full speed (100% duty cylce) opreation. Am I correct?

Braking by reverse motor current. Jacob had provided the explanation of how the PWM duty cycle controls the motor direction.

Ibrahim Burak Keskin said:

Also in the schematic in the typical application all mode selection inputs (MX) are set to 0. 

Mode set to 000 is fine for 2 full bridges or 4 indi half bridges. The parallel (double up) one full bridge is for driving one high current motor, which is not related to the typical mode 000.

Ibrahim Burak Keskin said:

Should I use the first operation mode (M2=0, M1=0) rather than fourth operation mode (M1=1, M2=1)? Because I believe that in this case, one has full control over H-bridge (two control signals for each H bridge). Though, I wondered if I can use the latter operation mode or not.

Both 000 and 011 modes are ok for driving motor bidirectional, but I would use mode 000 if the MCU has 4 pwm output pins, as mode 011 has half resolution for pwm control. 

Brian