Gripporillat
Well-known member
Hi there!
I'm designing a PCB with 39 digital and 46 analog inputs, 11 multiplexers (M74HC4851) a few more inputs and mosfet-switches and connectors for other devices. The board has a socket for a teensy 3.6 which is used as Midi USB Controller and controls the mosfets. The multiplexers are decoupled by one 0.1uF capacitor per multiplexer close to the VCC pin.
1. As far as I understand it is advisable to connect the analog inputs to analog GND on the teensy and the rest of the board to GND to minimize noise. What about the multiplexers? I could connect their GND pin to Teensy GND instead of AGND but this would lead to longer signal traces.
2. Since AGND and GND are connected within the teensy board it is better to not connect them externally to avoid ground loops. True?
3. I'm designing a 4 layer board where the first innner layer is reserved for ground planes. Since the layout of the board is mainly determined by the layout of the user interface it's kind of hard to properly divide separate the AGND plane from the DGND plane. This is what in my view would be possible:
Is it ok like this or would it be better to go for a single ground plane for all inputs?
Thank you in advance!
I'm designing a PCB with 39 digital and 46 analog inputs, 11 multiplexers (M74HC4851) a few more inputs and mosfet-switches and connectors for other devices. The board has a socket for a teensy 3.6 which is used as Midi USB Controller and controls the mosfets. The multiplexers are decoupled by one 0.1uF capacitor per multiplexer close to the VCC pin.
1. As far as I understand it is advisable to connect the analog inputs to analog GND on the teensy and the rest of the board to GND to minimize noise. What about the multiplexers? I could connect their GND pin to Teensy GND instead of AGND but this would lead to longer signal traces.
2. Since AGND and GND are connected within the teensy board it is better to not connect them externally to avoid ground loops. True?
3. I'm designing a 4 layer board where the first innner layer is reserved for ground planes. Since the layout of the board is mainly determined by the layout of the user interface it's kind of hard to properly divide separate the AGND plane from the DGND plane. This is what in my view would be possible:
Is it ok like this or would it be better to go for a single ground plane for all inputs?
Thank you in advance!