Datasheet

LPC11U6x 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 — 26 May 2014 81 of 96
NXP Semiconductors
LPC11U6x
32-bit ARM Cortex-M0+ microcontroller
14.6 RTC oscillator component selection
The 32 kHz crystal must be connected to the part via the RTCXIN and RTCXOUT pins as
shown in Figure 43
. 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 the 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
14.7 Connecting power, clocks, and debug functions
Figure 44 shows the basic board connections used to power the LPC11U6x, connect the
external crystal and the 32 kHz oscillator for the RTC, and provide debug capabilities via
the serial wire port.
Fig 43. RTC oscillator components
LPC1xxx
RTCXIN RTCXOUT
C
X2
C
X1
XTAL
=
C
L
C
P
R
S
L
aaa-010822