WEBENCH® Tools/MSP430F6779A: MSP430 Crystal Selection

Hi,

Actually, for F6779A, it has an internal capacitor, the default one is 1pF.

In the SLAA322D, it says the typical load capacitor is 6pF to 15 pF. The reason that it choose 12 pF is just for calculation.

I also check some datasheets for you, for some device, the internal capacitor can be 12pf, some can be 12.5pf. If you want to get a accurate frequency. I advice you to follow the oscillator datasheet.

  Eason

Thank you for your answer,

so I have additional some question,

1. I also calculating follow Application report “MSP430 32-kHz Crystal Oscillators” (SLAA322D).Could you please confirm , Am I calculated wrong?( crystal have load capacitance 12.5pF, XCAPx=0)

  2. Refer from No.1 from method doesn't have use 1pF (XCAPx =0), so for integrated effective load capacitance 1 pF, do we need 1pF use calculation?

Thank you

Refer from above question,

1. Am I calculated wrong?( crystal have load capacitance 12.5pF, XCAPx=0)

 Answer  Right.

2. Do we need 1pF use calculation? (XCAPx =0)

Answer   Yes, you need to put this into calculation. 

So, could you please suggest,

How to calculate effective load capacitance (CL1 and CL2) for use with integrated effective load capacitance 1 pF (XCAPx =0) ?  

 Calculate get 21pF but for capacitance from maker have 18pF and 22pF, so

1. Which 18pF or 22pF capacitance should I select?

2. Refer from question 1, why you select that values?

Thank you