I'm using a MAX3094ECSE+ RS-422/485 receiver receiver datasheet for an application that is receiving quadrature encoder wires. Those wires are power, positive and negative signals from quadrature external encoder. Encoder outputs are differential signals: A+, A-, B+, B-. They need, on the pcb, to be converted into A and B signals that will be connected to STM32F207ZG timer channel pins.
So I have used MAX3094ECSE for doing this. This was working fine on my protoboard prototypes, powered by a stable power source. But now I am facing the pcb design circuit. And now I was also wondering for the convenience or not of using a ferrite bead between my power circuit and this kind of device.
I'm not an expert using ferrite bead. But I know that it is often used for a better EMI isolation between analog and digital circuit, so I put ferrites between analog GND plane and digital GND plane. I know that ferrites are used in series with power leads when connected to high speed ICs, in ex: microcontrollers. As higher speed, a bypass capacitor should be also needed:
I don't know if quadrature encoder signals could be considered digital high speed signal or not. Furthermore I have to take into account the receiver output is going to microcontroller inputs. I'm not sure what kind of consideration I should have for the MAX receiver device, regarding this topic. Maybe the device needs it or maybe not.
Should I put ferrite bead between power 5V node and this Integrated Circuit Vcc pin? Could it work correctly without it here?
Could someone give me an answer to my question? if not, I hope to get his point of view.
NOTE: It is true that vendor doesn't suggest the use of ferrites with this device.
5V-power that powers 3 encoder and 2 MAX devices:
MAX device with no ferrite bead: