Please don't start a new thread each time.
By low capacitance probe how low ? 1pF ? thats 10% of the load capacitor. 12.000250MHz is +21ppm. So without probe load its even higher. The best way to measure a crystal frequency is either to output the clock on another pin, or just use a probe near but not connected to the crystal and a spectrum analyser.
I'm not sure from the plots I can understand the reference planes for all the signals. Each signal needs an adjacent return paths. It looks as though the flash signals are reference to the VCC plane a ground plane would be more conventional
Some of the decoupling capacitor don't appear to have a very small loop area. If layer 2 was a solid ground plane that would help and if the ground side of each decoupling capacitor had its own ground connection to the ground plane that would be good. You have use via in pad , I'd suggest that you do that for all the decoupling capacitors.
Try adding a 100R resistor on the SPI clock to ground on the bottom of the board under the flash chip incase the there is signal integrity issue.
By low capacitance probe how low ? 1pF ? thats 10% of the load capacitor. 12.000250MHz is +21ppm. So without probe load its even higher. The best way to measure a crystal frequency is either to output the clock on another pin, or just use a probe near but not connected to the crystal and a spectrum analyser.
I'm not sure from the plots I can understand the reference planes for all the signals. Each signal needs an adjacent return paths. It looks as though the flash signals are reference to the VCC plane a ground plane would be more conventional
Some of the decoupling capacitor don't appear to have a very small loop area. If layer 2 was a solid ground plane that would help and if the ground side of each decoupling capacitor had its own ground connection to the ground plane that would be good. You have use via in pad , I'd suggest that you do that for all the decoupling capacitors.
Try adding a 100R resistor on the SPI clock to ground on the bottom of the board under the flash chip incase the there is signal integrity issue.
Statistics: Posted by dp11 — Thu Jul 25, 2024 10:23 am