DRV8889-Q1: Hold time timing diagram

Hi

Hi David, please give me a day to look into this and get back. 

Hi Karan,

On the datasheet, the conditions for tH Hold time and tSU Setup time are both DIR to STEP rising. According to the literal meaning, there are three possibilities as follows. Which one is correct?

1.

2. Since the conditions are both DIR to STEP rising, can tH Hold time and tSU Setup time be combined together?

3.

Is it possible to switch directions while Step is running? (Change DIR signal)

Another question:

1. Are there any order requirements for DRVOFF and DIR?

2. Should DRVOFF go LOW before or after DIR? How long does it take?

3. How long before the STEP action does DRVOFF need to pull LOW?

4. How long does it take for DRVOFF to go High after the STEP action is completed?

Thanks & best regards,

Hi David, 

To answer your earlier question, the hold time is the minimum time you should wait for between a rising STEP edge and a change in DIR signal. In this case it is 200ns. 

I will take a look at the other questions tomorrow. Thank you.

-Karan

Hi David, 

David Yang said:

Is it possible to switch directions while Step is running? (Change DIR signal)

Yes, but make sure to wait for 200ns after each STEP rising edge before changing the DIR signal. Will get back to you on the DRVOFF question. 

-Karan

Hi Karan

Karan Doshi said:

Yes, but make sure to wait for 200ns after each STEP rising edge before changing the DIR signal

When the DIR signal meets the tSU Setup time, the DRV8889 has completed the direction change setting.

If the DIR signal changes within 200ns after the STEP rising edge, it may cause the DRV8889 to work abnormally.

Is it correct?

Thanks & best regards,

Hi Karan,

Karan Doshi said:

For DRVOFF, typically it must be set to OFF only when STEP pulses are stopped to ensure that current is decayed correctly.

Is there a timing diagram?

When DRVOFF is high, can the DIR signal be changed? 

Because the SW RnD requires the DRV8889 to operate at the correct timing, it ensures that the IC is working normally and will not cause abnormalities.

So we need to know the complete timing of DRVOFF, DIR and STEP. As shown below.

Thanks & best regards,

David Yang said:

When the DIR signal meets the tSU Setup time, the DRV8889 has completed the direction change setting.

If the DIR signal changes within 200ns after the STEP rising edge, it may cause the DRV8889 to work abnormally.

Is it correct?

Thanks & best regards,

Correct, if the DIR signal changes within 200ns of the STEP rising edge, performance may be abnormal. 

David Yang said:

Is there a timing diagram?

We do not spec this parameter, David. This will require a few weeks of time to get this information. Meanwhile, can you please help me understand why the customer is doing a DRVOFF? This looks unusual.

David Yang said:

When DRVOFF is high, can the DIR signal be changed? 

Yes. DRVOFF = high corresponds to outputs disabled. DIR can be changed.

Hi Karan,

Karan Doshi said:

Meanwhile, can you please help me understand why the customer is doing a DRVOFF? This looks unusual.

Customer's RnD responded that they would turn off the motor, so the MCU has control over DRVOFF to turn on/off the motor.

Karan Doshi said:

We do not spec this parameter, David. This will require a few weeks of time to get this information

Could you kindly give us a clearly time?

In addition to the timing of STEP to DRVOFF (set off). Is there a time interval required between DRVOFF (High -> Low) and STEP?

Thanks & best regards,

David Yang said:

Customer's RnD responded that they would turn off the motor, so the MCU has control over DRVOFF to turn on/off the motor.

What is wrong with using the sleep mode to turn off the motor? This request seems a little unusual. Let me get back to you on the timeline. 

David Yang said:

In addition to the timing of STEP to DRVOFF (set off). Is there a time interval required between DRVOFF (High -> Low) and STEP?

Like I said, David, we do not spec timings for DRVOFF. As mentioned earlier, it is recommended not to use DRVOFF for interruption in motor's general operation. Current decay may not be proper. I will get back to you with a timeline on all the parameters you have asked for, if that is indeed something that we can provide. If not, we will recommend an alternative way. 

Regards,
Karan

Hi David, I have raised a help ticket to get these parameters you have asked for. Timeline is about a week or two. 

Regards,
Karan

Hi Karan,

Do you have any update ? 

Thanks & best regards,

Hi,

Thank you for your question. May 27th Monday is national holiday in US. Will feedback to expert back office

Hi David, 

Please give me a day to look into this and get back to you. 

Regards,
Karan

Hi David, 

The Jira ticket is in works. Will take some time. Let me ask the design team and get back to you about this with an updated timeline. Thanks for your patience.

Regards,
Karan

Hi Karan

Do you have any update ? 

Thanks & best regards,

Hi David, 

Design team still working on this. Can you share which customer this is for, if not here then on email? (k-doshi@ti.com) Might help me expedite the ticket resolution. 

Regards,
Karan