Datasheet

LPC11E6X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 1.2 — 21 May 2014 74 of 89
NXP Semiconductors
LPC11E6x
32-bit ARM Cortex-M0+ microcontroller
keep the noise coupled in via the PCB as small as possible. Also parasitics should stay as
small as possible. Smaller values of C
x1
and C
x2
should be chosen according to the
increase in parasitics of the PCB layout.
14.5 RTC oscillator component selection
The 32 kHz crystal must be connected to the part via the RTCXIN and RTCXOUT pins as
shown in Figure 40
. If the RTC is not used, the RTCXIN pin can be grounded.
Select C
x1
and C
x2
based on the external 32 kHz crystal used in the application circuitry.
The pad capacitance C
P
of the RTCXIN and RTCXOUT pad is 3 pF. If load capacitance of
the external crystal is C
L
, the optimal C
x1
and C
x2
can be selected as:
C
x1
= C
x2
= 2 x C
L
– C
P
14.6 Connecting power, clocks, and debug functions
Figure 41 shows the basic board connections to power the LPC11E6x, to connect an
external crystal and the 32 kHz oscillator, and provide debug capabilities.
Fig 40. RTC oscillator components
LPC1xxx
RTCXIN RTCXOUT
C
X2
C
X1
XTAL
=
C
L
C
P
R
S
L
aaa-010822