Datasheet

LPC408X_7X All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 3.1 — 1 September 2014 76 of 138
NXP Semiconductors
LPC408x/7x
32-bit ARM Cortex-M4 microcontroller
7.36.4.4 Deep power-down mode
The Deep power-down mode can only be entered from the RTC block. In Deep
power-down mode, power is shut off to the entire chip with the exception of the RTC
module and the RESET
pin.
To optimize power conservation, the user has the additional option of turning off or
retaining power to the 32 kHz oscillator. It is also possible to use external circuitry to turn
off power to the on-chip regulator via the V
DD(REG)(3V3)
pins and/or the I/O power via the
V
DD(3V3)
pins after entering Deep Power-down mode. Power must be restored before
device operation can be restarted.
The LPC408x/7x can wake up from Deep power-down mode via the RESET
pin or an
alarm match event of the RTC.
7.36.4.5 Wake-up Interrupt Controller (WIC)
The WIC allows the CPU to automatically wake up from any enabled priority interrupt that
can occur while the clocks are stopped in Deep-sleep, Power-down, and Deep
power-down modes.
The WIC works in connection with the Nested Vectored Interrupt Controller (NVIC). When
the CPU enters Deep-sleep, Power-down, or Deep power-down mode, the NVIC sends a
mask of the current interrupt situation to the WIC. This mask includes all of the interrupts
that are both enabled and of sufficient priority to be serviced immediately. With this
information, the WIC simply notices when one of the interrupts has occurred and then it
wakes up the CPU.
The WIC eliminates the need to periodically wake up the CPU and poll the interrupts
resulting in additional power savings.
7.36.5 Peripheral power control
A power control for peripherals feature allows individual peripherals to be turned off if they
are not needed in the application, resulting in additional power savings.
7.36.6 Power domains
The LPC408x/7x 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.
On the LPC408x/7x, I/O pads are powered by V
DD(3V3)
, while V
DD(REG)(3V3)
powers the
on-chip voltage regulator which in turn provides power to the CPU and most of the
peripherals.
Depending on the LPC408x/7x application, a design can use two power options to
manage power consumption.
The first option assumes that power consumption is not a concern and the design ties the
V
DD(3V3)
and V
DD(REG)(3V3)
pins together. This approach requires only one 3.3 V power
supply for both pads, the CPU, and peripherals. While this solution is simple, it does not
support powering down the I/O pad ring “on the fly” while keeping the CPU and
peripherals alive.