DRV8703-Q1: fault at -40degC

Domenico,

How do you disable the VDS monitor feature?

Hi Wang,

the customer is disabling the monitor feature through register 0x04h as per table 22 in the datasheet,

regards,

Domenico

Domenico,

How do you confirm the fault condition? When the failure is happened, would you read 0x00h, 0x01h and 0x04h register value?

Domenico,

After discussing it with our senior engineer, I can give more clues.
1. Even the VDS protection feature is disabled, the fault register will still report the overcurrent status according to VDS threshold setting. But, nFault pin won't be pulled low.
2. Even the VDS status change, the device should not stop working. So, it could be another issue. Let us read all register values.
3. After VDS is disabled. If the load current is too high, another OCP is still there to prevent the short condition.
"In addition to this FET VDS monitor, an overcurrent condition is detected if the voltage at the SP pin exceeds VSP(OCP) and the nFAULT pin is driven low. The OCP bit in the DRV8703-Q1 device is set." Please check nFault pin voltage to confirm it.

Hi Wang,

thanks for the clarifications.
The cstomer will be able to do other test on monday morning. I'll be there in the lab. If you need any other info or you can provide me with other hints on what I have to check in the lab please let me know.
The shunt connected to VSP is 4mohm, so I home that in the mosfet are not flowing 200A.

regards,
Domenico

Hi Wang,

I've been in the lab to make some other test on the device.

I've noticed that when the temperature reaches -40degC the DRV8703-Q1 is not able to drive anymore the motor. The device resets its register and so we are not able to detect the presence of a fault. Unfortunately the nfault pin is connected to the uC but not monitored yet.

I've attached some screenshot of the current of the bridge. The DRV is working at 100% duty cycle, 12V.

From the screenshot you can see the the current goes to 0 for some time.

In order to double check if the issue is related to the board of the customer we have used the EVM of the DRV8703-Q1, but the GUI seems having a bug. When you configure the registers and you switch to control page (enable the motor) and  then you  go back to registers tab the registers show always the default value.

So we were not able to verify with the EVM the issue seen in the customer EVM.

Can you also check if the GUI has any bug ?

regards,

Domenico

Acquisizioni DRV8703-Q1.zip

Domenico

Domenico,

1. What do you measure in your attached waveform? The offset is about -1.5V. What is it?
2. "when the temperature reaches -40degC the DRV8703-Q1 is not able to drive anymore the motor" I saw a switching waveform after stop swithcing 100ms. So, "not able to drive anymore the motor" means motor not moving or no switching.
3. “When you configure the registers and you switch to control page (enable the motor) and then you go back to registers tab the registers show always the default value.” Yes. For DRV8703 GUI, when we switch from "register map" page to "motor control page", the registers are reset to the default value. So, we have to enable the motor in motor control first.