DRV3946-Q1: Unable to get two IC working

Hello Devendra,

Thanks a lot for the question

Can you please help me with the schematics of the board.

Also can you provide a waveform of the SPI transactions after the inital power up(including SCLK, nSCS, SDO and SDI)

Thanks,
Ibinu

Hello Ibinu, Below are schematics for both drivers :

Also I am providing the below initialization waveform for init state and broadcast

We were expecting the output 2 should be high and when we send closure command the output should get transition from high to low, but the status of output2 is low as can be seen in below graph and when we request for closure, driver get enabled as per EN1 transit to high but no change in output 2 and when we send open command the is spike for few microseconds and driver will get disable. 

Hi Devandra,

Thank you for the captures. I will review them and get back to you tomorrow.

Best,

Keerthi

Hi Devandra,

Any progress on your side. I have started reviewing, I will comment tomorrow morning. 

Best,

Keerthi

Hello Keerthi,

The issue of not detecting both driver is solved with new hardware sample somehow (there was no change in schematic though, PCB layout was changed)

But still second issue with variable duty value for 4th contactor is still there. 

If possible then I will share more communication details. 

Also, we have 3 IC for DRV3901 on same SPI channel in which still issue preset with detection of NAD and probably it will be HW issue for NAD register similar to DRV3946. 

But I would like to know more on the process of Broadcast command and Override command, why and when we need it and probable root cause for using it. Because in previous sample (development samples) NAD was not detecting properly, and I had to use Broadcast command as well as NAD override command too to get detection of NAD. But later samples, we don't need it and with normal initialization sequence both NAD got detected. 

Thanks,

Devendra

Hi Devandra,

By variable duty cycle, is the duty cycle changing over time or is it fixed? Can you take a capture of the load current, IPROPI, and Output Voltage.

What is the contactor resistance, PVDD, and the hold current setting you are using?

Can you send a picture of the top side of the development samples?

Best,

Keerthi

Hello Keerthi, duty is continuously getting changed. Currently I don't have accesso to main setup with contactor connected hence at this moment I am not able to provide you requested values. 
Below are configuration Register values (XX are CRC value calculated at run time and no CRC warning present). Both driver have same configuration.

Thanks.

Devendra

Hi Devandra,

Just to clarify a few more things:

Are you forcing a constant duty cycle or setting it to current regulation:

Maybe we can have a quick call to discuss this to expedite the debug. I am located in Dallas so feel free to send a time that works for you.

Best,

Keerthi

Hello Keerthi,

We have set CHX_CTRL_COFIG as 0 and when we are setting 0x2 (Internal current regulation) value when closing contactor.
First issue seems to be resolved due to HW bug and mostly probably 2nd issue might be resolved once we get actual contactor with latest HW. 

If this issue still exists, I will schedule call with you. [expected time frame is 1 week ]

Thanks,

Devendra

Hi Devendra,

let me review once and get back to you.

best,

Keerthi