I am using a FS4500 as a SBC for a KEA (KEAZ128) MCU, the FS4500's VCORE is connect to KEA's VDD, and FS4500's VCCA is connect to KEA's VDDA. I have a problem when I power on the FS4500, the Vcore and Vcca are not stable while power on reset, you can see the waveform in the attachment file.
This problem can be solve if I use FS4500 Vcore only to provide 5V for KEA's VDD and VDDA.
Does any one know why can't I give independent 5V to KEA from FS4500?
There is almost zero load on the VCCA.
And when I use SBC's VDD only as the 5V source to power on the KEA MCU, we found the slew rate is different on the Vcore and Vcca.
You can see the waveform, the Vcca is fast than Vcore.