The LPC1759 is a Cortex-M3 microcontroller for embedded applications featuring a high level of integration and low power consumption at frequencies of 120 MHz

LPC1759FBD80

Manufacturer Part NumberLPC1759FBD80
DescriptionThe LPC1759 is a Cortex-M3 microcontroller for embedded applications featuring a high level of integration and low power consumption at frequencies of 120 MHz
ManufacturerNXP Semiconductors
LPC1759FBD80 datasheet
 


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NXP Semiconductors
7.28 RTC and backup registers
The RTC is a set of counters for measuring time when system power is on, and optionally
when it is off. The RTC on the LPC1759/58/56/54/52/51 is designed to have extremely low
power consumption, i.e. less than 1 A. The RTC will typically run from the main chip
power supply, conserving battery power while the rest of the device is powered up. When
operating from a battery, the RTC will continue working down to 2.1 V. Battery power can
be provided from a standard 3 V Lithium button cell.
An ultra-low power 32 kHz oscillator will provide a 1 Hz clock to the time counting portion
of the RTC, moving most of the power consumption out of the time counting function.
The RTC includes a calibration mechanism to allow fine-tuning the count rate in a way
that will provide less than 1 second per day error when operated at a constant voltage and
temperature.
The RTC contains a small set of backup registers (20 bytes) for holding data while the
main part of the LPC1759/58/56/54/52/51 is powered off.
The RTC includes an alarm function that can wake up the LPC1759/58/56/54/52/51 from
all reduced power modes with a time resolution of 1 s.
7.28.1 Features
Measures the passage of time to maintain a calendar and clock.
Ultra low power design to support battery powered systems.
Provides Seconds, Minutes, Hours, Day of Month, Month, Year, Day of Week, and
Day of Year.
Dedicated power supply pin can be connected to a battery or to the main 3.3 V.
Periodic interrupts can be generated from increments of any field of the time registers.
Backup registers (20 bytes) powered by VBAT.
RTC power supply is isolated from the rest of the chip.
7.29 Clocking and power control
7.29.1 Crystal oscillators
The LPC1759/58/56/54/52/51 include three independent oscillators. These are the main
oscillator, the IRC oscillator, and the RTC oscillator. Each oscillator can be used for more
than one purpose as required in a particular application. Any of the three clock sources
can be chosen by software to drive the main PLL and ultimately the CPU.
Following reset, the LPC1759/58/56/54/52/51 will operate from the Internal RC oscillator
until switched by software. This allows systems to operate without any external crystal and
the bootloader code to operate at a known frequency.
See
Figure 4
LPC1759_58_56_54_52_51
Product data sheet
LPC1759/58/56/54/52/51
for an overview of the LPC1759/58/56/54/52/51 clock generation.
All information provided in this document is subject to legal disclaimers.
Rev. 7 — 29 March 2011
32-bit ARM Cortex-M3 microcontroller
© NXP B.V. 2011. All rights reserved.
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