Nxp Semiconductors UM10237 用户手册

UM10237_2

© NXP B.V. 2008. All rights reserved.

 

 gives the crystal parameters that should be used. C

L

 is the typical load 

capacitance of the crystal and is usually specified by the crystal manufacturer. The actual 
C

L

 influences oscillation frequency. When using a crystal that is manufactured for a 

different load capacitance, the circuit will oscillate at a slightly different frequency 
(depending on the quality of the crystal) compared to the specified one. Therefore for an 
accurate time reference it is advised to use the load capacitors as specified in 

 that belong to a specific C

L

. The value of external capacitances C

X1

 and 

C

X2

 specified in this table are calculated from the internal parasitic capacitances and the 

C

L

. Parasitics from PCB and package are not taken into account.

 

11 pF

< 100 k

Ω

18 pF, 18 pF

13 pF

< 100 k

Ω

22 pF, 22 pF

15 pF

< 100 k

Ω

27 pF, 27 pF

RTCX1

RTCX2

C

X1

C

X2

32 kHz

Xtal