DRV8701: nFAULT pin low impedance

Hi Jason,

nFAULT pin is an open-drain pin meaning it is hi-z when no fault is present. Its impedance to device GND should be very high not in the range of what you measured. However, when a fault is present, nFAULT is pulled to GND via a FET. 

Can you provide answers to the following questions:

1. Can you provide more information as to how the impedance measurement was taken? was the device ON or powered? Was the impedance taken with respect to drv GND?
2. If measurement was taken when device is powered ON and device awake, what is the voltage at nFAULT pin?
3. Is it possible to provide schematic of driver stage?
4. Was this low impedance detected on ALL devices from customer or only the ones given to you?

Regards,

Pablo Armet

Hi Pablo,

Thanks for your reply.

1. I used a multimeter to measure nFAULT impedance (nFault to drv GND) at the device power off.

2. Due to impedance really low so nFAULT voltage is still low when device on.

3. May I send the schematic by E-mail?

4. Low impedance only happened on the return box (RMA), not all devices.

Regards,

Jason

Hi Jason,

Yes. Please share the schematic via private message. 

Regards,

Pablo Armet

Hi Pablo,

I already send schematic by private message.

Please help to review it, thanks.

Regards,

Jason

Thanks Jason!  Pablo will follow-up.