OM11077 NXP Semiconductors, OM11077 Datasheet - Page 81

• Manufacturer Part Number: OM11077
• Description: MODULE DIMM LPC2478 ARM7
• Manufacturer: NXP Semiconductors

Specifications of OM11077

• Accessory Type: Module Card
• For Use With/related Products: ARM-57TS-LPC2478
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 568-4742

NXP Semiconductors
LPC2478
Product data sheet
14.4 RTC 32 kHz oscillator component selection
Table 22.
The RTC external oscillator circuit is shown in
integrated on chip, only a crystal, the capacitances C
externally to the microcontroller.
Table 23
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 23.
Fundamental oscillation
frequency F
15 MHz to 20 MHz
Crystal load capacitance
C
11 pF
20 MHz to 25 MHz
13 pF
15 pF
Fig 29. RTC oscillator modes and models: oscillation mode of operation and external
L
L
influences oscillation frequency. When using a crystal that is manufactured for a
gives the crystal parameters that should be used. C
crystal model used for C
Recommended values for C
components parameters): high frequency mode
Recommended values for the RTC external 32 kHz oscillator C
OSC
All information provided in this document is subject to legal disclaimers.
RTCX1
C X1
LPC2xxx
32 kHz XTAL
Rev. 2 — 29 September 2010
L
Maximum crystal series
resistance R
< 100 kΩ
< 100 kΩ
< 100 kΩ
Crystal load
capacitance C
10 pF
20 pF
10 pF
20 pF
. The value of external capacitances C
RTCX2
C X2
X1
/C
X2
X1
S
/C
evaluation
L
X2
in oscillation mode (crystal and external
Maximum crystal
series resistance R
< 180 Ω
< 100 Ω
< 160 Ω
< 80 Ω
Figure
Single-chip 16-bit/32-bit microcontroller
X1
=
29. Since the feedback resistance is
External load capacitors C
18 pF, 18 pF
22 pF, 22 pF
27 pF, 27 pF
and C
L
X2
is the typical load
S
need to be connected
L
C L
R S
X1
and C
External load
capacitors C
18 pF, 18 pF
39 pF, 39 pF
18 pF, 18 pF
39 pF, 39 pF
002aaf495
LPC2478
© NXP B.V. 2010. All rights reserved.
X1
C P
/C
L
X2
. Parasitics
X2
specified in
components
Table 23
X1
X1
,
/C
81 of 91
CX2
X2