User Manual - Philips LPC2101 User Manual

Philips Semiconductors
Volume 1
Table 201
capacitance of the crystal and is usually specified by the crystal manufacturer. The actual
C
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
this table are calculated from the internal parasitic capacitances and the C
from PCB and package are not taken into account.
Table 201: Recommended values for the RTC external 32 kHz oscillator C
Crystal load capacitance
C
11 pF
13 pF
15 pF

User manual

Fig 59. RTC 32 kHz crystal oscillator circuit
gives the crystal parameters that should be used. C
influences oscillation frequency. When using a crystal that is manufactured for a
L
L
Rev. 01 — 12 January 2006
LPC2101/02/03
RTXC1 RTXC2
32 kHz
C
X1 Xtal
. The value of external capacitances C
L
Maximum crystal series
resistance R
S
< 100 kΩ
< 100 kΩ
< 100 kΩ
UM10161
Chapter 17: RTC
C
X2
is the typical load
L
and C specified in
X1 X2
. Parasitics
L
components
X1/X2
External load capacitors C
18 pF, 18 pF
22 pF, 22 pF
27 pF, 27 pF
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Table 201
,
X1 CX2
224