propa
Well-known member
Hi,
Long time since I've been here last! My friend criticised my board layouts in the past due to neglecting to take into consideration return currents, stating that ideally you want a clear path underneath the signal, as return current flows underneath the board.
I've read a few things about path of least resistance and path of least impedance for high speed signals, but I'm unclear whether this would actually affect layouts for Codecs for example. Do the signals for the audio codecs eg MCLK LRCLK, BLCK run at such a speed where a designer really needs to pay attention to return current paths?
In practice I'm trying to route a board for the CS42448, as I found that the Teensy library supports it. I've read the datasheet, and does mention to leave the Clock signals away from the FLIT+ parts to avoid coupling into the modulators (https://www.mouser.com/datasheet/2/76/CS42448_F4-275685.pdf page 39)
The datasheet also states to leave a copper pour under the IC with vias connected to ground plane on other side of of board. If you were to fill the entire space under the bottom of the IC with a copper pour, then routing signals becomes a bit more complex, as LRCLK and BCLK need to be connected to two sides of the chip, it's easier to route if you connect to those two under the chip.
So I guess my question or invitation for advice would be along the lines of; there's no avoiding signals will eventually cross, especially on smaller boards, but how much and when does it matter for audio? Should I just be concerned with return current on the main power signals, or every single signal? Does it really matter about bottom traces running perpendicular to another signal on the top?
It's just a bit of criticism, but it's really hindered my ability to finish anything off now, as I'm 2nd guessing every trace and decision. I'd really like to get some reassurance or people's personal takes/intuition/advice etc
Cheers in advance and apologies if this isn't directly Teensy related, but there's an amazing wealth of knowledge and you've all been really great at disseminating information, so I hope it's not too out of place. TIA!
Long time since I've been here last! My friend criticised my board layouts in the past due to neglecting to take into consideration return currents, stating that ideally you want a clear path underneath the signal, as return current flows underneath the board.
I've read a few things about path of least resistance and path of least impedance for high speed signals, but I'm unclear whether this would actually affect layouts for Codecs for example. Do the signals for the audio codecs eg MCLK LRCLK, BLCK run at such a speed where a designer really needs to pay attention to return current paths?
In practice I'm trying to route a board for the CS42448, as I found that the Teensy library supports it. I've read the datasheet, and does mention to leave the Clock signals away from the FLIT+ parts to avoid coupling into the modulators (https://www.mouser.com/datasheet/2/76/CS42448_F4-275685.pdf page 39)
The datasheet also states to leave a copper pour under the IC with vias connected to ground plane on other side of of board. If you were to fill the entire space under the bottom of the IC with a copper pour, then routing signals becomes a bit more complex, as LRCLK and BCLK need to be connected to two sides of the chip, it's easier to route if you connect to those two under the chip.
So I guess my question or invitation for advice would be along the lines of; there's no avoiding signals will eventually cross, especially on smaller boards, but how much and when does it matter for audio? Should I just be concerned with return current on the main power signals, or every single signal? Does it really matter about bottom traces running perpendicular to another signal on the top?
It's just a bit of criticism, but it's really hindered my ability to finish anything off now, as I'm 2nd guessing every trace and decision. I'd really like to get some reassurance or people's personal takes/intuition/advice etc
Cheers in advance and apologies if this isn't directly Teensy related, but there's an amazing wealth of knowledge and you've all been really great at disseminating information, so I hope it's not too out of place. TIA!