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Multiple nFAULT DRV8803
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mrburnzie:
Hi everyone!
I'm working a project where I have multiple DRV8803 ICs for solenoid driving.
The DRV8803 has a nFAULT pin, which is used for over temperature/current monitoring.
I'm using 16 channel i2C MUX to control them from my MCU.
I'm running out of pins when I add all the INPUT channels (4), plus the nFAULT pin.
I'm controlling one solenoid at the time (the time difference between activation of two solenoids can be minutes to hours).
Could I tie all nFAULT pins together (or group them into 4-8) and monitor that pin?
By the datasheet nFAULT is "Logic low when in fault condition", so I think that it would work without a problem, because I know which solenoid is from which exact driver and I can determine where the fault is coming from.
Datasheet: https://www.ti.com/lit/ds/symlink/drv8803.pdf?ts=1593275378760&ref_url=https%253A%252F%252Fwww.ti.com%252Fmotor-drivers%252Fsolenoid%252Foverview.html
Stay safe!
mikerj:
The nFAULT output is open drain so you can safely tie all your nFAULT outputs together with a single pull-up resistor.
mrburnzie:
Thanks for confirming. Cheers! 8)
Simon:
looks like someone goofed up on that datasheet copy and pasting from one of the many other DRV88xx drivers. I can't see how that driver woueli work for a stepper motor the way the show as the outputs are open drain not tri state totem-pole.
Siwastaja:
Yes, fault output pins are almost always open-drain just because of this reason: you often want to save pins and ease routing by treating all faults equally, without needing to know where the fault is coming from. This is especially handy if your fault handling is a discrete logic circuitry and not an MCU, you don't then need a large OR gate.
Just remember the pull-up resistor or it won't work!
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