I did some searching here and elsewhere on the net and only found a few mentions of this sensor but nothing too useful.
The datasheet says “optimized for low-side current sensing”, but am I correct in thinking that this can be used inline so the ADC can be read at any time rather than synchronizing with PWM?
Can I ignore the fault pin? It sounds annoying. It latches and won’t clear unless you cycle the power. The datasheet doesn’t say whether the output continues functioning with the fault tripped. It also doesn’t say whether the pullup resistor is required for the chip to function. The schematic shows a weak internal pull-down, so I’m hoping I can just leave the pin disconnected.
The datasheet shows a capacitor CLOAD on the output pin, but no mention of what would be an appropriate value for it. Any ideas? The Pololu breakout board doesn’t have a capacitor on the output at all.
I used this on my lemon-pepper boards. In my case it was a bad part pick, because I wanted an all-in-one board and the hall sensors can pick up magnetic field from the motor which is mounted to the back of the PCB.
Yes, with 0A current the output is centered on 1/2 Vcc, so it can resolve current in both directions so it can be used inline. I think I took this from the ratiometry plot on pg. 13. Because it is a hall sensor it has quite high Vcm (I think this is the 100V quoted on the first page, I didn’t see a specific Vcm spec in the document)
I left this disconnected in my schematic, but I also never tripped it. I don’t know if latching disables output but I would hope not, since for most closed loops systems that would cause a runaway current if it looked like there was none flowing, making the problem worse.
I set CLOAD to 100n. I think the intent might be to form an RC filter on Vout if you don’t need the full 100kHz bandwidth?
Thank you! That sounds like it should be ok for my use, since I have the drivers centrally mounted. Most of the time the closest motor is 35mm away, although one can get within 25mm in certain positions. These are 2208 motors.
However I did notice a potential problem with proximity of the sensors to eachother. I’m trying to cram them in on the back side of my Gooser without significantly increasing the board dimensions, but since the plan is to have two boards mounted back-to-back with 1.8mm tall ceramic capacitors and copper bars inbetween, the current sensors are actually very close to the surface of the other board… sensing element maybe 1.3mm from other current-carrying copper. Not sure if that’s enough to cause problems or if I should move them to the top side at the cost of 5mm more board length.