Note that it isn't a zener on the Pico, it's a Schottky diode. The very small voltage drop across it might explain your results, or might be coincidence.
A couple of things look wrong on this.
Running those MCP2515 from 5V violates the maximum rating for the Pico's GPIOs - you have MISO and INT as 5V signals feeding in to the RP2040 GPIOs which is not allowed. The pullup to 5V on CS1/CS2 has the same problem. Possibly you can fix this by running the MCP2515 from 3V3 and just the transceivers from 5V, but I haven't checked.
10uF looks rather small for C12 (input capacitor for the 7805), given your series inductors in the supply. No doubt the ripple is small as you have measured, but what about the response to large transients (such as the CAN Tx turning on)? The Pico is somewhat protected by the buck-boost supply for the 3V3, but that will further decrease the stability around the 5V regulation (as the voltage dips, the current will go up).
A couple of things look wrong on this.
Running those MCP2515 from 5V violates the maximum rating for the Pico's GPIOs - you have MISO and INT as 5V signals feeding in to the RP2040 GPIOs which is not allowed. The pullup to 5V on CS1/CS2 has the same problem. Possibly you can fix this by running the MCP2515 from 3V3 and just the transceivers from 5V, but I haven't checked.
10uF looks rather small for C12 (input capacitor for the 7805), given your series inductors in the supply. No doubt the ripple is small as you have measured, but what about the response to large transients (such as the CAN Tx turning on)? The Pico is somewhat protected by the buck-boost supply for the 3V3, but that will further decrease the stability around the 5V regulation (as the voltage dips, the current will go up).
Statistics: Posted by arg001 — Wed Nov 13, 2024 4:47 pm