TMS320F28035-EP: TMS320F28035

Hi,

Prasanth Ram Jothikumar said:

The error comes only when I turn on power stage. Plus, the CCS gets startled to read any instuctions, including a muse click. After referring the CCS forum, I installed all the drivers for emultion package recommended form TI website; but was not succesfull. Having suspected the EMI issue, the controller is completely isolated with EMI tape, still couldnt be succesfull, can anyone help me out here?

Do you have an oscilloscope so that you can watch the communication signals? 

It sounds like this is a big EMI noise problem. That would help confirm this suspicion.  

Best Regards,

Ben Collier

Hello Expert Mr.Benjamin Collier,

Thanks a lot for helping me out, may I know, what signals you want to check? This would help me to find the issue.

Also, I would ike to ask you that, we have just used an capacitor to isolate controller ground between power stage ground, and control signals. So, do you think that not using a seperate isolator could also be an issue here? 

Many thanks

Ram 

Ram,

Sorry, I meant to ask for you to check the JTAG signals. TMS, TCK, TDI, TDO and TRST.

Prasanth Ram Jothikumar said:

So, do you think that not using a seperate isolator could also be an issue here? 

Are controller ground and power stage ground connected in any way other than this capacitor? So are they effectively disconnected for DC? 

I don't think this would cause the issue that you're seeing above, but I'm not sure if this would cause any other issue.

Best Regards,

Ben Collier

Dear Mr.Benjamin, 

Please find the waveform attached herewith, these waveforms are taken while power stage is off. From evalautions, I wasnt able to see 3.3V in any of the pins (TMS, TCK, TDI, TDO and TRST) -Image 1. But then, for the same code on TI reference design, I could able to see 3.3 V (Image 2).

I seek your sinciere advice in this regard. 

Ram

Ram,

Prasanth Ram Jothikumar said:

Please find the waveform attached herewith, these waveforms are taken while power stage is off. From evalautions, I wasnt able to see 3.3V in any of the pins (TMS, TCK, TDI, TDO and TRST) -Image 1.

Is the F28035 device powered on at this point? 

Prasanth Ram Jothikumar said:

But then, for the same code on TI reference design, I could able to see 3.3 V (Image 2).

The TI reference design will have pullup resistors on these signals (pulldown on TRST). There should even be internal pullup resistors on these pins. I am surprised that you are seeing them tied low unless the device is now powered on.

Anyway, I wanted to see if there was noise at the point that you lose communication, which would be after the power stage is turned on.

Best Regards,

Ben Collier

Dear Expert Mr.Benjamin, 

thanks a lot for explaining the difference between TI reference design and customised converter design. Indeed, it was a new knowledge for me. 

Benjamin Collier said:

The TI reference design will have pullup resistors on these signals (pulldown on TRST). There should even be internal pullup resistors on these pins. I am surprised that you are seeing them tied low unless the device is now powered on.

As you suspected there is a huge noise in the JTAG pins. The converter is designed for 12 A, and untill 0.5 A, the noise in JTAG is minimal, Please refer image 1. Rising the current to 1 A creates a huge noise in JTAG (please refer image 2). Would like to hear from you for the suggestion.

Many thanks,

Ram