Confused about DRV8432 in parallel mode

fmvalero

Hi,

I'm planning to use the DRV8432 for controlling a DC motor with a maximum current of 12A. So I need to use he DRV8432 in pararell mode. But, after readind the post 'DRV8432DKD cycle-by-cycle current limit' (http://e2e.ti.com/support/applications/motor_drivers/f/38/t/133322.aspx?pi239031349=2), I'm quite confused. Can I control the motor with a PWM signal in PWM_A and GND in PWM_B? Because, in principle, that's the way to do it. But, if I have understood correctly what it is said in the post, controlling like that causes that the DRV8432 is stuck when the output hits CBC limit.

In pararell mode I can't use the OC latched mode and I need to have control over the maximum current. So, is the only way to control the motor to connect a PWM signal to one input and the complementary PWM signal to the other input? Can I have any problem if I do it this way?

That is, if I want to use the parallel mode and to have the cycle-by-cycle current limit working correctly, how have I to manage the inputs?

Thanks,

Fernando.

over 12 years ago

0 Ryan Kehr over 12 years ago

TI__Guru 55715 points

Fernando,

Actually, you are not confused at all. Your understanding is correct and the post you referenced details the issue. CBC mode relies on a switching input in both channels as a rising edge is required to "wake up" a channel that goes into current limit. The device remains in OC until the next cycle. If that never comes, than the device is stuck in current limit and half-bridge is disabled.

You will have no problem if you use complimentary inputs.

0 fmvalero over 12 years ago in reply to Ryan Kehr

Prodigy 40 points

OK, thaks for your answer. I have another question. The current limit is independent for each output. Does that mean that if you set OC_ADJ at 7.4 A, you are actually limiting current at 14.8 A? Because each half bridge is managing half of the total current that is going through the motor.

0 fmvalero over 12 years ago in reply to fmvalero

Prodigy 40 points

Please, could you answer this question? I very important to me in order to decide as soon as possible whether I can use the DRV8432 in my design.

0 Ryan Kehr over 12 years ago in reply to fmvalero

TI__Guru 55715 points

That is basically correct. Although, this assumes perfect current sharing between the half-bridges. Best to assume that you may have 10% more in one bridge over the other and set Radj accordingly.

0 fmvalero over 12 years ago in reply to Ryan Kehr

Prodigy 40 points

Okay, everything is clear now..

Thank you very much for your help.

Motor drivers

Motor drivers forum

Confused about DRV8432 in parallel mode