MCT8316Z: Schematic review

Hi Aaron,

The nFAULT connection test with external 3.3V instead of VBK shows no change in behavior.

Please check if there are any other problems.

If there is anything needed for analysis, I will ask the customer.

Thank you for your support.

Hi Cho,

Can you confirm nSLEEP = 1 and DRVOFF = 0? Does customer see ~10mA of nominal current for the MCT8316Z when it is in idle mode vs sleep mode? 

Has the customer spun the motor yet with this device or has not gotten it to work yet?

Thanks,
Aaron

Hi 

nSLEEP = High, DRVOFF = Low fixed.

nominal current : 5.18mA

The motor does not operate at all, not even a "tick" sound.

Hi Cho,

Today is a holiday in the US, I will get back to you tomorrow.

Thanks,
Aaron

Hi Cho, 

Apologize I did not get back to this. Can you share layout?

Thanks,
Aaron

Hi Aaron,

I asked the customer for a layout. Please wait.

Hi Aaron,

I attached the layout file.

Request is being checked.

gbr.pdf

Hi Cho,

I don't have many concerns with the layout. Only two comments I have are:

1) CPH-CPL cap is a little far, check if VCP = VM+5V to ensure charge pump is working sufficiently
2) PGND traces have some thin inductance/impedance for motor current path, make sure that motor current for each phase can travel through the thin trace and back to the PGND ground plane and back to the supply. Check if impedance/inductance is added from the PGND pin at the device to the negative of the supply. 

In regards to AVDD, can you check the impedance of AVDD-GND with respect to a known good MCT8316Z0T device? Maybe AVDD exceeded the 30-mA limit and damaged from there being two 0-ohm resistors for the hardware resistors (VSEL_BK, ADVANCE, MODE, SLEW). 

Thanks,
Aaron

Hi Aaron,

Update the customer's answers.

Please give me some advice to solve the problem.

1) Can we check the powerup sequence of the MCU vs VM? 

-> VM will power on first.

2) If the VM powerup is strange, can the ferrite bead be removed and shorted?

-> VM output appears to be fine.

3) Can you check the soldering of the AVDD pin on the package? The best way to tell if the soldering is bad is measuring the continuity from the AVDD bypass cap to the AVDD pin, it should be a short. 

-> AVD pin solder is fine.

4) Is this occurring on multiple boards or just 1 board?

-> Just 1 board

5) When powering the MCT8316Z, can you monitor on an oscilloscope:

- VCP (should be 5V above VM)
- VM
- nFAULT (should be at 3.3V before VM goes above VM_UVLO)
- VBK (should be 3.3V at powerup)

-> Both VCP and VM are output at 19V.

nFAULT is coming in late.

nFAULT does not reach 3.3 V before the VM reaches VM_UVLO.

VBK 6V output.

Hi Aaron,

The customer is going to SWAP test when the MCT8316Z sample arrives.

I will reply to you later after the case is closed.