Hi Team,
For the external clock, a crystal will be used, the total capacitance is 9pF to get 16MHz, the parasitic input capacitance for XTAL1 and XTAL2 pins may have an effect on such low capacitance. So could you please tell the parasitic input capacitance of XTAL1 and XTAL2 pins? Thanks!
Best Regards!
Hao
Hao,
You can use the IBIS model to help determine the input capacitances for those pins. The model can be found here:
An explanation for the IBIS model can be found here:
The models for input (XTAL1) and output (XTAL2) pins are similar but look like this:
Typical values for the R_pkg, L_pkg, and C_pkg are for both pins:
R_pkg 0.0925Ω
L_pkg 2.0385nH
C_pkg 0.4168pF
For the C_comp values, I would use:
XTAL1 C_comp: 1.078pF
XTAL2 C_comp: 1.633pF
In total, the input capacitance would be about:
XTAL1: 1.5pF
XTAL2: 2 pF
Joseph Wu
