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 37 of 96
NXP Semiconductors
LPC11U6x
32-bit ARM Cortex-M0+ microcontroller
8.25.2 Power domains
The LPC11U6x provide two independent power domains that allow the bulk of the device
to have power removed while maintaining operation of the RTC and the backup registers.
The VBAT pin supplies power only to the RTC domain. The RTC requires a minimum of
power to operate, which can be supplied by an external battery. The device core power
(V
DD
) is used to operate the RTC whenever V
DD
is present. Therefore, there is no power
drain from the RTC battery when V
DD
is available and V
DD
 VBAT + 0.3 V.
8.25.3 Integrated oscillators
The LPC11U6x include the following independent oscillators: the system oscillator, the
Internal RC oscillator (IRC), the watchdog oscillator, and the 32 kHz RTC oscillator. Each
oscillator can be used for more than one purpose as required in a particular application.
Following reset, the LPC11U6x operates from the internal RC oscillator until software
switches to a different clock source. The IRC allows the system to operate without any
external crystal and the bootloader code to operate at a known frequency.
See Figure 10
for an overview of the LPC11U6x clock generation.
Fig 11. Power distribution
REAL-TIME CLOCK
BACKUP REGISTERS
WAKE-UP
CONTROL
REGULATOR
32 kHz
OSCILLATOR
ALWAYS-ON/RTC POWER DOMAIN
MAIN POWER DOMAIN
RTCXIN
VBAT
VDD
RTCXOUT
VDD
VSS
to memories,
peripherals,
oscillators,
PLLs
to core
to I/O pads
ADC
TEMP SENSE
ADC POWER DOMAIN
VDDA
VSSA
LPC11U6x
ULTRA LOW-POWER
REGULATOR
WAKEUP
aaa-010818