• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 98 subscribers
  • Views 314 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Reg - Crystal(CS325-24.000MABJ-UT) in reference board for OSC0

Manoj Agarwal
Expert 1030 points
Other Parts Discussed in Thread: AM3352

Hi,

I have below query for CS325-24.000MABJ-UT selected in reference board.

1. How 18PF valus is calculated. Our values is coming close to 26pF so considering limit we can chose 24pF.

Cl(Load capacitance)=18pF as per Crystal datasheet, Cs(Shunt capacitance)=5pF( 5pF of Crystal) .

Considering C1 and C2 of same value.

18 = C/2+5

C=26pF. Hence C1=C2= 26pF.

As per availability and minimum requirement from AM3352 specs requirement 24pF capacitor is chosen.

2.  ESR = 80 ohm of  CS325-24.000MABJ-UT is not matching with required limit.

Regards

Manoj A

  • 0
    Genius 3685 points

    My formula is:

    if you have a crystal with a load capacitance of 18pF, then 18pF * 2 = 36pF.

    For each pin, subtract 7pF for layout capacitance and pin capacitance.

    36 - 7 = 29pF. So I would start with 1 capacitor of 27pF and 1 capacitor of 33pF.

    In my designs, I use crystals with 13pF load capacitance. Some low-power oscillators in modern CPU have problems with higher load capacitance.

    13pF load capacitance gives you 2 capacitors of 18pF.

    Fine tuning is done by measurement.