DRV8832: Motor diver issue

Hi Cherry,

Cherry Zhou said:

1. when the motor is spinning, IN1 and IN2 inputs are high at the same time, causing the motor to brake, but the motor will not brake as expected. The FAULTn pin can detect that it is pulled low.

Can you provide a scopeshot showing at least VOUT1, VOUT2, IOUT, and nFAULT when INx=HIGH and when one of the inputs is pulled LOW? Set the trigger point to falling edge of nFAULT. Also, provide a zoomed in waveform and a zoomed out waveform.

Cherry Zhou said:

2. when the chip is in the initial state of IN1 and IN2 input high simultaneously, pull one of the pins low and the motor will not start. The motor can only be rotated by pulling one of the pins high when the initial state is IN1 and IN2 input low.

Again, can you please provide waveforms of both cases, Show IN1, IN2, VOUT (which ever corresponds to the INx going LOW), nFAULT.

Cherry Zhou said:

4. when the IN1, IN2 inputs are one high, one low, normally control the motor rotation, there is a certain probability that the motor will stop abnormally, test IN1 and  IN 2 with an oscilloscope, the input does not change but OUT1, OUT2 no longer outputs the voltage. And this phenomenon only occurs in one direction of motor rotation, not in both directions where the motor may stop abnormally. When the motor stops abnormally, the FAULTn pin output may be low or may still be high-impedance.

Has this behavior seen in multiple ICs or is it isolated to only one IC? Is replacing the populated IC with a new one solve the issue? Another test you can try to confirm if this is an IC issue or motor related issue, please use different motors (preferably ones with higher resistance). I'm curious if this fault is repeatable. 

Hi,

Figure1: Yellow wire 1: Motor drives chip output pin Green line 4: Fault foot Blue Line 2, Violet Line 3: Motor drive chip input pin

The motor input pin is 1 high 1 low at the beginning, the motor is spinning normally, and the Fault pin and output pin signals are good. Pull the input feet high to expect the motor to brake. The actual VOUT voltage has a rising process, after about 800us, the Fault pin signal output is low, the VOUT signal becomes abnormal, and the actual motor stops spinning.

Figure 2: Yellow line 1: Motor drive current signal Blue Line 2: Motor drives chip input pin. Purple Line 3: Motor drives chip output pin Green line 4: Fault foot

Same state as Figure 1, except measurement signal: Motor drive chip output voltage and current signals are good at the beginning of normal motor rotation. Pull the input foot high to expect the motor to brake. The actual motor current goes up in reverse, with the Fault pin signal output low after approximately 800us and the VOUT signal stops. The actual motor stops spinning.

Figure 3: Yellow line 1: Motor drive chip output pin Blue Line 2, Violet Line 3: Motor drive chip input pin Green line 4: Fault foot

Following the braking operation of Figures 1 and 2, the Fault pin output is low and the motor drive chip input is high. Motor drive chip output is low, motor is in stop state; pull one of the input signals low, desired effect: Motor starts to spin. The actual motor does not start and the Fault signal and output signal remain low.

Pablo Armet said:

Has this behavior seen in multiple ICs or is it isolated to only one IC? Is replacing the populated IC with a new one solve the issue? Another test you can try to confirm if this is an IC issue or motor related issue, please use different motors (preferably ones with higher resistance). I'm curious if this fault is repeatable. 

It has been tested on multiple devices (multiple ICs, multiple motors), and this fault is repeatable.

Thanks and Best Regards,

Cherry

Hi Dear,

May I know is there any updates?

Thanks and Best Regards,

Cherry

Hi Cherry,

I'm still working on this. Please give me some more time and I will back to you soon.

Hi Pablo,

Noted and thanks for your support!

Thanks and Best Regards,

Cherry

Hi Cherry,

Quick update. I'm still working on this. I will send a reply by the end of day today.

Hi Cherry,

Apologies again for the late reply. The output voltage seems to be very noisy even when motor is supposed to be in normal operation. I wonder if this is somehow being caused by the motor. Can you do the following quick tests to verify:

1. Repeat the previous tests with no load and with a resistivity load. If the noise is present, then it could be a layout or other system related problem. If this is the case, we'll have to look at the layout in more detail.

This device only has three main protection features. They are shown below. We can go one by one to figure out which fault is being triggered. Can you answer the following questions:

1. Is the VCC signal stable during the motor braking operation?
2. The current spikes above 1-A close to 1.3-A which is the minimum OCP threshold. It is probable that an OCP fault was triggered. Can you zoom into the regions where nFAULT drops LOW and show the current near this region.\
3. I doubt this is thermal shutdown since it automatically recovers. After each fault, does the motor completely stop requiring a VCC power cycle? If so, this is most likely an OCP fault. To verify, you can monitor the device temperature.

Hi Pablo,

Thanks for your hard-working on this issue! I have forwarded to the customer and please expect some new info.

Thanks and Best Regards,

Cherry

Cherry,

Thanks. Let me know when you hear back from customer.

Hi Pablo,

Here's some updates:

Pablo Armet said:

Is the VCC signal stable during the motor braking operation?

Yes, VCC signal is stable.

Pablo Armet said:

The current spikes above 1-A close to 1.3-A which is the minimum OCP threshold. It is probable that an OCP fault was triggered. Can you zoom into the regions where nFAULT drops LOW and show the current near this region.\

The waveform is as follows:

The yellow portion is the output current, the current peak is almost 1.3 A.

Pablo Armet said:

I doubt this is thermal shutdown since it automatically recovers. After each fault, does the motor completely stop requiring a VCC power cycle? If so, this is most likely an OCP fault. To verify, you can monitor the device temperature.

Could you please elaborate what do you mean by this?

Thanks and Best Regards,

Cherry