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I'm designing an application for this mangetic angular sensor https://www.monolithicpower.com/Portals/0/Documents/Position%20Sensors/datasheet_MA700_rev1.2.pdf Because this is precise and sensitive piece, I'm thinking if I should have additional VCC filtering. Any thoughts welcome!

This sensor IC will sit on a tiny PCB, which will be connected to main controller board with SPI flat cable. Should I place capacitor on the main board just before the cable? Should I place capacitor on the tiny PCB? Should I have inductor in addition to capacitor? Should I not worry about it at all?

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Put the capacitor as close to the device as possible on the small board. You might want a series inductor (also on the small board before the capacitor). Do not omit the 100nF capacitor shown in the datasheet, put that capacitor closest to the part and a larger capacitor a little further away from the sensor chip than the 100nF (1uF is probably a good choice if you are not sure).

All of this depends on the amount of conducted EMI on the power input wires.

If the power is really bad, put a higher voltage on the power input to the board (possibly 5V) and put a high PSRR LDO on the small board to generate the 3.3V power rail for the sensor chip.

Shielded cable and connectors are probably a better solution than an additional capacitor and inductor.

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This sensor IC will sit on a tiny PCB, which will be connected to main controller board with SPI flat cable.

Whenever possible, interleave low-amplitude analog signals on a flat-cable between GND's. Although it requires more space on the PCB to fit a larger connector, this provides a shielding for the signal, particularly useful if the cable has lengh restriction.

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  • \$\begingroup\$ Doesn't this introduce ground loop? \$\endgroup\$ Mar 14 at 15:31

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