Crystal Load Capacitance calculation incorrect

[FreshmanNewbie]

I am using this device (https://ww1.microchip.com/downloads...Sheets/USB251xB-xBi-Data-Sheet-DS00001692.pdf)

On page 44 of the datasheet, they have given the formula to calculate the crystal load capacitance.

I have a crystal. It's datasheet mentions that it's load capacitance is 6pF and Shunt capacitance is 3pF.
And considering 3pF for CB1 and Cxtal of 6pF (mentioned in the pin capacitance table), CS1 = 3pf + 6pf = 9pf.
If I substitute CS1 in the formula,
C1 = 2*(CL - Co) - CS1
CL = 6pf
Co = 5pf

C1 = 2*(6pf - 5pf) - 9pf
C1 = 2pf - 9pf
C1 = -7pf

I am getting negative capacitor values for the load capacitances.

Am I missing something or doing incorrectly.

So, does this crystal not support this device?

 

[FvM]

As mentioned in the datasheet:

C0 is usually included (subtracted by the crystal manufacturer) in the specification for C L and should be set to 0 for use in the calculation of the capacitance formula

It also doesn't seem right to put in the maximum value of Cxtal.

 

[FreshmanNewbie]

As mentioned in the datasheet:

It also doesn't seem right to put in the maximum value of Cxtal.

It is for worst case calculation, I need to put the maximum value of Cxtal. Please help whether the selected crystal having the CL and C0 are fine?

 

[FvM]

Load capacitance should be selected for typical rather than maximal external capacitance values to achieve best frequency matching.

As stated, shunt capacitance will be usually ignored in load capacitance calculation because it's already included in the specified target load capacitance.