drv88432 Fast Decay, Slow decay

ALbert Tello

Intellectual 735 points

Other Parts Discussed in Thread: DRV8412DDWEVM

Is any documentation on Fast-Slow decay for the drv8432 .

Slow Decay:

Can be used in the following combination

Drive:

A= PWM, B=0

~A=0 ~B=PWM

Slow Decay :

A = 0 B=0

A=1 ~B=1,

~B will be =1 all the time , is any concern doing this for the drv8432.

2) Is any different way to use Fast Decay than Resetting AB and CD ?

3) I would like to know in which c file in the drv8412EVM REVG the decay is controlled to see hay is done at 4000 steps per second

Albert

over 11 years ago

0 Rick Duncan over 11 years ago

TI__Guru** 114905 points

Hi Albert,

Can you clarify which EVM you have? There are two in the eStore:

1) The DRV8412-C2-KIT and
2) The DRV8412DDWEVM

Thanks.

0 ALbert Tello over 11 years ago in reply to Rick Duncan

Intellectual 735 points

Hi Rick

We have both in the office, in the ticket I refer to DRV8412-C2-KIT, that came the the software from TI

Albert

0 ALbert Tello over 11 years ago in reply to ALbert Tello

Intellectual 735 points

_{Hi Rick}

We use the demo came with EVM , I would like to know how is hnadle Fast-Slow Decay in the demo.

Could you please inform me where can I find decay control for the Stepper Motor.

Albert

0 Rick Duncan over 11 years ago in reply to ALbert Tello

TI__Guru** 114905 points

Hi Albert,

I have notified the group that develops the firmware. You should receive a response soon.

If not, you can also post to the C2000 forum. There is more information regarding the code there.

http://e2e.ti.com/support/microcontrollers/c2000/default.aspx

0 ALbert Tello over 11 years ago in reply to Rick Duncan

Intellectual 735 points

Hi Rick

I would like to ask if you can speed up if the firmware team can inform me where Decays is handle in the software demo.

Also where can get the dynamics parameters from the wheel diodes in each FET. The reason our algorithms needs to calculate in Low decay the I(t) for the current.

We are close to production, I love to have the answers soon.

Thank you Rick for your support

Albert

0 Rick Duncan over 11 years ago in reply to ALbert Tello

TI__Guru** 114905 points

Hi Albert,

We are still trying to determine the decay information. Sorry for the delay.

Can you provide more details regarding the dynamic parameters of the diodes? What specific parameters that you are interested?

0 Rick Duncan over 11 years ago in reply to Rick Duncan

TI__Guru** 114905 points

Hi Albert,

The DRV8412-C2-KIT does not perform a traditional decay mode. It uses a pid loop to determine the PWM duty cycle required to meet the current requirements. Once determined, one output is held low and the other output is PWM'ed in at the determined duty cycle. Once the PWM'ed output has been driven high to meet the desired duty cycle, the PWM'ed output is then driven low to create a slow decay.

I cannot provide more details than this. The code is the documentation for this example.

Do you have the list of specific parameters you are interested in?

0 ALbert Tello over 11 years ago in reply to Rick Duncan

Intellectual 735 points

Hi Rick

Thank you for your answers, I found how the current in controlled.

I have only one question in regards Drain to Source Diode the bulk resistance (series resistance to Diode conduction).

Mostly in all Diode are close to 1 Ohm , Is safe to assume 1 Ohm

Albert

Thank you again Rick again for your support

0 Rick Duncan over 11 years ago in reply to ALbert Tello

TI__Guru** 114905 points

Hi Albert,

Is the information you are after shown in Figure 4 of the datasheet?

Once the diode turns on, the resistance is shown as approximately 50mOhms (using .8 to 1V, and 1 to 5 A). Before that the resistance from .6 to .8, 0 to 1A works out to be 200mOhms.

Looks like depending on how you are using the 1Ohm, it is very conservative.

0 ALbert Tello over 11 years ago in reply to Rick Duncan

Intellectual 735 points

Thank you Rick

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drv88432 Fast Decay, Slow decay