Other Parts Discussed in Thread: AFE4403
I am checking the hardware by newly manufacturing a circuit using AFE4490. The signal line of AFE4490 connected to CPU such as MSP430 is not connected.
SPIMOSI, SPIMISO, SCK , LED-ALM and so on.
Even if an 8MHz crystal oscillator and a capacitor of 18pF are connected to the AFE4490, the oscillation waveform cannot be observed at the Xout terminal.
Using 4.7pF, 10pF, 22pF, I was able to oscillate this 8MHz crystal oscillator with 74HCU04.
Since it was possible to oscillate with all capacitors, the crystal oscillator is normal and the load capacitance of 18pF is also appropriate.
For checking the inverter and 1/2 frequency divider circuit inside the AFE4490,
I connected the 8MHz clock oscillated by 74HCU04 to the Xin terminal.
When I observed the 4MHz clock terminal, there are times when the 4MHz clock can be observed and times when it cannot be observed.
I cannot see the 4MHz waveform constantly. Please refer to attached waveform.
The possible causes are as follows.
1. The drive capacity of the inverter inside the AFE4490 is weak and cannot oscillate.
2.74HCU04 and AFE4490 have different inverters, so it cannot oscillate with the same capacitor.
3. The inverter or 1/2 frequency divider circuit is out of order.
If you have any other possible causes, please let me know.
