BLDC controller

Mikael Sundberg

Other Parts Discussed in Thread: DRV8301

Hi,

I really need some input.

We have developed our own BLDC controller cpmpletely based on the schematics for the DRV8301-HC-EVM. Now there is a problem that OCTW asserts low as soon as the DRV8301 is enabled from the F28069M processor. This occurs with or without motor attached. The FETs are ok and all connections are tripple checked. It is correct as far as we can see. This fault actually occurs even with completely detached FETs. What could be the reason for this? We certainly don't have any overcurrents. Is the chip faulty?

Thank you for any ideas!

/Mikael

over 9 years ago

0 Mikael Sundberg over 9 years ago

Intellectual 730 points

Update,
I can also confirm that changing to a new drv8301 results in the same error after a small squeel in the motor using lab2c. I am completely out of ideas.

Br,
Mikael

0 Rick Duncan over 9 years ago in reply to Mikael Sundberg

TI__Guru** 114905 points

Hi Mikael,

Please check the buck connections. There have been reports of problems with the buck causing the device to overheat. This can cause nOCTW to assert.

See LINK for an example.

0 Nicholas Oborny over 9 years ago in reply to Mikael Sundberg

TI__Mastermind 21320 points

MIkael,

If you refer to the datasheet there are several reasons nOCTW may assert.

As Rick mentioned overtemperature is one of them.

If you heard noise from the motor, this almost sounds like an overcurrent event. This would not be resolved by removed the MOSFETs and the driver will now see a large voltage across the VDS sense when it "enables" the MOSFET.

Can you get scope captures of when nOCTW occurs and compare against the input and output PWM signals.

0 Mikael Sundberg over 9 years ago in reply to Mikael Sundberg

Intellectual 730 points

This issue was caused by a small short at the pcb.

0 Mikael Sundberg over 9 years ago in reply to Mikael Sundberg

Intellectual 730 points

I changed the drv8301 again on this pcb. Now it is just consuming more power than before and gets warm as soon as powered up. I have changed it twice and still get this result. What else might result in this warm up? Are there any other component likely to fail when the drv8301 failed? Now it seems like the new drv8301 is broken directly at power up or enable. Still it provides 5V. Any ideas?

0 Nicholas Oborny over 9 years ago in reply to Mikael Sundberg

TI__Mastermind 21320 points

Mikael,

This sounds like some sort of short circuit. Can you inspect for any issues? Do you see this problem on other PCBS? Can you give more details about what kind of current you expect and what you are seeing.

0 Mikael Sundberg over 9 years ago in reply to Nicholas Oborny

Intellectual 730 points

When the DRV8301 has reported a fault the drv8301 starts to consume about 150mA when idle. This is at least twice as much as before the fault appears. We have big issues with our layout after first error occured. I only wanted to know if there were any known problems that could be after a driver failure due to short in the mosfets, other than the drv8301. The design is almost identical to the schematics of DRV8301-HC-EVM, so I was referring to this in my thoughts.

0 Nicholas Oborny over 9 years ago in reply to Mikael Sundberg

TI__Mastermind 21320 points

Mikael,

I am not sure. I would recommend checking pins to ensure correct voltages are present and trying to determine what the fault is and where the current is going.

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