Extended teensy-like board

[techniqq]

Hello,
I am currently designing a custom PCB based on a Teensy 4.0 schematic and I would kindly like to ask for your feedback before sending it to manufacturing. In my design, I have added external PSRAM and Flash memory, an ICM20948 IMU for which I am routing a dedicated SPI bus, as well as an LM35 temperature sensor.


Before proceeding, I would like to make sure that everything is connected correctly and that the board is likely to work reliably. In particular, I would greatly appreciate any comments regarding the PSRAM and Flash connections, the additional SPI routing for the ICM20948, and the overall power and grounding layout. I want to ensure that I have not overlooked any important details that could cause issues later.


Thank you very much in advance for your time and assistance.

 

[MarkT]

No full ground-plane layer? With 8 layers you should be able to have several continuous ground and power planes to keep EMC under control and have plenty of signal routing left...

 

[techniqq]

No full ground-plane layer? With 8 layers you should be able to have several continuous ground and power planes to keep EMC under control and have plenty of signal routing left...

I had trouble getting all the necessary pins out of the MCU without using all the layers I am a hobbyist and have no professional experience about these things.

 

[BriComp]

I would suggest you look at the TMP117 for the temperature sensor. Much more accurate and easier to use being I2C.
No worries about voltage conversion, noise etc.

 

[PaulStoffregen]

The most common strategy for PCB routing is to dedicate some layers for horizontal and other layers for vertical traces. Usually long diagonal lines are avoided until almost everything is routed with only vertical and horizontal lines, because a long diagonal line tends to become an obstacle for routing more traces. After everything is routed with only horizontal and vertical and you're sure nothing more will need to be added, then it's easy to see which traces can become shorter and more direct diagonal lines.

 

[techniqq]

I really appreciate all your responses.

1. It's a school project and I have to use the LM35.
2. Okay, I will reroute my PCB following these rules.

Apart from that, did I make any mistakes in the power-up sequence routing? I would really appreciate it if this board worked on the first try.

 

[PaulStoffregen]

did I make any mistakes in the power-up sequence routing?

By first glance at your schematic, looks like you have the same 3 diode circuit.

But I hope you can understand how difficult it is for me or anyone else to help check this style of schematic. Almost all your connections are with net names which appear to be the BGA pin numbers, rather than readable names or wires showing the actual connection. For anyone to try checking requires a lot of tedious checking of the BGA pinout.