DRV8706S-Q1EVM: Motor driver error

Hi Danilo,

By default the DVDD supply is regulated from the PVDD supply. 

When only the USB connection is present, we're likely back-driving the MSP430 through the UART pins, and the DVDD rail.  The desired power sequence in this case is to always supply PVDD first, then connect USB.  Admittedly this is a bit clunky when you are going through regular PVDD power cycles because this means also disconnecting the USB connection).

If we wish to power DVDD from the USB connection, and avoid the back-driving scenario, R77 can be removed, and installed in position R75.

When the status LED is not lit, try pressing the reset button on the EVM after the supplies are properly connected.  This should clear the fault as well.

We can also check the IC_STAT_2 register, and confirm the source of the under-voltage fault.  Likely it is PVDD.  In this case, it is probably a situation where the bulk cap is still charging while the voltage monitors are active, and the PVDD is fault is triggered.  The PVDD fault can be configured to automatically recover, such that the fault clears automatically when PVDD rises above the minimum threshold.  This can be configured in the UVOV_CTRL register.

Regards,
Mike

Hello Michael,

I make all advice for you but still nothing.nFault still active.

I make some measurement on the board to try understand what have this behavior and I find that Charge Pump voltage of the driver is deactivated.

At CP output nothing happened.

Than I try to clear CLR_FLT but can't be clear.It set again after reset.

Also I try to change VCP_UV_MODE from Latched Fault mode to Automatic Recovery Mode but same behavior, after I change any register value are put immediately to default value.

VCP_UV fault stay set no mather what o try to do.

What else I can verify or perform? Do you think driver can enter in a loop and deactivate internal CP ?

If you can help me,what I can do will be very helpfully for me because I already has a week delay from my test on DRV8706 driver that company think to used in future for drive the motors.

Thanks you!

Have a nice day!

Hi Alberto,

Sorry you're having some troubles.  This doesn't sound normal.  The EVM includes a probe point for VCP near U1.  Can you send a scope trace showing your supply and VCP ramping?  For this test you should be able to leave USB disconnected.

Regards,
Mike

Hello Michael,

Thank you for your support.

I perform tests and attached scope capture with traces.

Voltage from VCP (out 30 of driver) is in yellow and Vsupply taken from EVM power J1 are in blue.

VCO try to start but immediately stop.

Same behavior has CPH and CPL.

Do you think it is an driver issue?

I can remove R1 resistance from the board to see if issue is from the driver or from circuit around him.

What do you think?

Thanks you!

Alberto,

Thank you for the scope traces - let me talk to some folks here before you modify your board.  I will get back with you tomorrow.

Regards,
Mike

Alberto,

Still working on an explanation on your observations here.  Do you have only one EVM?

Regards,
Mike

Alberto,

Let me temporary close this post since MIke takes off this week. if you have some updates needs to put into this thread, you can post it after thanksgiving.