Datasheet

LPC15XX All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
Product data sheet Rev. 1 — 19 February 2014 45 of 99
NXP Semiconductors
LPC15xx
32-bit ARM Cortex-M3 microcontroller
8.35 Power domains
The LPC15xx 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 and V
DD
>= VBAT + 0.3 V.
8.36 Integrated oscillators
The LPC15xx 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 multiple purposes.
Following reset, the LPC15xx 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 14
for an overview of the LPC15xx clock generation.
Fig 15. 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
ACMP
DAC
INTERNAL
VOLTAGE REF
ADC POWER DOMAIN
VDDA
VSSA
LPC15xx
ULTRA LOW-POWER
REGULATOR
WAKEUP
aaa-010876