Datasheet

LPC2141_42_44_46_48 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 5 — 12 August 2011 37 of 45
NXP Semiconductors
LPC2141/42/44/46/48
Single-chip 16-bit/32-bit microcontrollers
In slave mode the input clock signal should be coupled by means of a capacitor of 100 pF
(Figure 12
), with an amplitude between 200 mV (RMS) and 1000 mV (RMS). This
corresponds to a square wave signal with a signal swing of between 280 mV and 1.4 V.
The XTAL2 pin in this configuration can be left unconnected.
External components and models used in oscillation mode are shown in Figure 13
and in
Table 10
and Table 11. Since the feedback resistance is integrated on chip, only a crystal
and the capacitances C
X1
and C
X2
need to be connected externally in case of
fundamental mode oscillation (the fundamental frequency is represented by L, C
L
and
R
S
). Capacitance C
P
in Figure 13 represents the parallel package capacitance and should
not be larger than 7 pF. Parameters F
OSC
, C
L
, R
S
and C
P
are supplied by the crystal
manufacturer.
Fig 12. Slave mode operation of the on-chip oscillator
Fig 13. Oscillator modes and models: oscillation mode of operation and external crystal
model used for C
X1
/C
X2
evaluation
Table 10. Recommended values for C
X1
/C
X2
in oscillation mode (crystal and external
components parameters): low frequency mode
Fundamental oscillation
frequency F
OSC
Crystal load
capacitance C
L
Maximum crystal
series resistance R
S
External load
capacitors C
X1
/C
X2
1 MHz to 5 MHz 10 pF < 300  18 pF, 18 pF
20 pF < 300  39 pF, 39 pF
30 pF < 300  57 pF, 57 pF
LPC2xxx
XTAL1
C
i
100 pF
C
g
002aae718
002aag469
LPC2xxx
XTAL1 XTAL2
C
X2
C
X1
XTAL
=
C
L
C
P
R
S
L