Datasheet

LPC11E1X All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 1.1 — 24 September 2013 22 of 62
NXP Semiconductors
LPC11E1x
32-bit ARM Cortex-M0 microcontroller
7.16.2 System PLL
The PLL accepts an input clock frequency in the range of 10 MHz to 25 MHz. The input
frequency is multiplied up to a high frequency with a Current Controlled Oscillator (CCO).
The multiplier can be an integer value from 1 to 32. The CCO operates in the range of
156 MHz to 320 MHz. To support this frequency range, an additional divider keeps the
CCO within its frequency range while the PLL is providing the desired output frequency.
The output divider can be set to divide by 2, 4, 8, or 16 to produce the output clock. The
PLL output frequency must be lower than 100 MHz. Since the minimum output divider
value is 2, it is insured that the PLL output has a 50 % duty cycle. The PLL is turned off
and bypassed following a chip reset. Software can enable the PLL later. The program
must configure and activate the PLL, wait for the PLL to lock, and then connect to the PLL
as a clock source. The PLL settling time is 100 s.
7.16.3 Clock output
The LPC11E1x feature a clock output function that routes the IRC oscillator, the system
oscillator, the watchdog oscillator, or the main clock to an output pin.
7.16.4 Wake-up process
The LPC11E1x begin operation by using the 12 MHz IRC oscillator as the clock source at
power-up and when awakened from Deep power-down mode . This mechanism allows
chip operation to resume quickly. If the application uses the main oscillator or the PLL,
software must enable these components and wait for them to stabilize. Only then can the
system use the PLL and main oscillator as a clock source.
7.16.5 Power control
The LPC11E1x support various 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 can also be controlled as needed by
changing clock sources, reconfiguring PLL values, and/or altering the CPU clock divider
value. This power control mechanism allows a trade-off of power versus processing speed
based on application requirements. In addition, a register is provided for shutting down the
clocks to individual on-chip peripherals. This register allows fine-tuning of power
consumption by eliminating all dynamic power use in any peripherals that are not required
for the application. Selected peripherals have their own clock divider which provides even
better power control.
7.16.5.1 Power profiles
The power consumption in Active and Sleep modes can be optimized for the application
through simple calls to the power profile. The power configuration routine configures the
LPC11E1x for one of the following power modes:
Default mode corresponding to power configuration after reset.
CPU performance mode corresponding to optimized processing capability.
Efficiency mode corresponding to optimized balance of current consumption and CPU
performance.
Low-current mode corresponding to lowest power consumption.
In addition, the power profile includes routines to select the optimal PLL settings for a
given system clock and PLL input clock.