LPC1766_0.02
© NXP B.V. 2008. All rights reserved.
Objective data sheet
Rev. 00.02 — 12 August 2008
32 of 70
NXP Semiconductors
LPC1766
Fast communication chip
The Wake-up Timer monitors the crystal oscillator to check whether it is safe to begin
code execution. When power is applied to the chip, or when some event caused the chip
to exit Power-down mode, some time is required for the oscillator to produce a signal of
sufficient amplitude to drive the clock logic. The amount of time depends on many factors,
including the rate of VDD(3V3) ramp (in the case of power on), the type of crystal and its
electrical characteristics (if a quartz crystal is used), as well as any other external circuitry
(e.g., capacitors), and the characteristics of the oscillator itself under the existing ambient
conditions.
7.29.6 Power control
The LPC1766 supports a variety of power control features. There are four special modes
of processor power reduction: Sleep mode, Deep-sleep mode, Power-down mode, and
Deep power-down mode. The CPU clock rate may also be controlled as needed by
changing clock sources, reconfiguring PLL values, and/or altering the CPU clock divider
value. This allows a trade-off of power versus processing speed based on application
requirements. In addition, Peripheral Power Control allows shutting down the clocks to
individual on-chip peripherals, allowing fine tuning of power consumption by eliminating all
dynamic power use in any peripherals that are not required for the application. Each of the
peripherals has its own clock divider which provides even better power control.
Integrated PMU (Power Management Unit) automatically adjust internal regulators to
minimize power consumption during Sleep, Deep sleep, Power-down, and Deep
power-down modes.
The LPC1766 also implements a separate power domain to allow turning off power to the
bulk of the device while maintaining operation of the RTC and a small set of registers for
storing data during any of the power-down modes.
7.29.6.1
Sleep mode
When Sleep mode is entered, the clock to the core is stopped. Resumption from the Sleep
mode does not need any special sequence but re-enabling the clock to the ARM core.
In Sleep mode, execution of instructions is suspended until either a Reset or interrupt
occurs. Peripheral functions continue operation during Sleep mode and may generate
interrupts to cause the processor to resume execution. Sleep mode eliminates dynamic
power used by the processor itself, memory systems and related controllers, and internal
buses.
7.29.6.2
Deep-sleep mode
In Deep-sleep mode, the oscillator is shut down and the chip receives no internal clocks.
The processor state and registers, peripheral registers, and internal SRAM values are
preserved throughout Deep-sleep mode and the logic levels of chip pins remain static.
The output of the IRC is disabled but the IRC is not powered down for a fast wake-up later.
The RTC oscillator is not stopped because the RTC interrupts may be used as the
wake-up source. The PLL is automatically turned off and disconnected. The CCLK and
USB clock dividers automatically get reset to zero.
The Deep-sleep mode can be terminated and normal operation resumed by either a
Reset or certain specific interrupts that are able to function without clocks. Since all
dynamic operation of the chip is suspended, Deep-sleep mode reduces chip power
consumption to a very low value. Power to the flash memory is left on in Deep-sleep
mode, allowing a very quick wake-up.
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