PIC18F2420/2520/4420/4520
1.1.2
MULTIPLE OSCILLATOR OPTIONS
AND FEATURES
1.0
DEVICE OVERVIEW
This document contains device-specific information for
the following devices:
All of the devices in the PIC18F2420/2520/4420/4520
family offer ten different oscillator options, allowing
users a wide range of choices in developing application
hardware. These include:
• PIC18F2420
• PIC18F2520
• PIC18F4420
• PIC18F4520
• PIC18LF2420
• PIC18LF2520
• PIC18LF4420
• PIC18LF4520
• Four Crystal modes, using crystals or ceramic
resonators
• Two External Clock modes, offering the option of
using two pins (oscillator input and a divide-by-4
clock output) or one pin (oscillator input, with the
second pin reassigned as general I/O)
This family offers the advantages of all PIC18
microcontrollers – namely, high computational perfor-
mance at an economical price – with the addition of
high-endurance, Enhanced Flash program memory.
On top of these features, the PIC18F2420/2520/4420/
4520 family introduces design enhancements that
make these microcontrollers a logical choice for many
high-performance, power sensitive applications.
• Two External RC Oscillator modes with the same
pin options as the External Clock modes
• An internal oscillator block which provides an
8 MHz clock and an INTRC source
(approximately 31 kHz), as well as a range of
6 user-selectable clock frequencies, between
125 kHz to 4 MHz, for a total of 8 clock
1.1
New Core Features
frequencies. This option frees the two oscillator
pins for use as additional general purpose I/O.
1.1.1
nanoWatt TECHNOLOGY
All of the devices in the PIC18F2420/2520/4420/4520
family incorporate a range of features that can signifi-
cantly reduce power consumption during operation.
Key items include:
• A Phase Lock Loop (PLL) frequency multiplier,
available to both the High-Speed Crystal and Inter-
nal Oscillator modes, which allows clock speeds of
up to 40 MHz. Used with the internal oscillator, the
PLL gives users a complete selection of clock
speeds, from 31 kHz to 32 MHz – all without using
an external crystal or clock circuit.
• Alternate Run Modes: By clocking the controller
from the Timer1 source or the internal oscillator
block, power consumption during code execution
can be reduced by as much as 90%.
Besides its availability as a clock source, the internal
oscillator block provides a stable reference source that
gives the family additional features for robust
operation:
• Multiple Idle Modes: The controller can also run
with its CPU core disabled but the peripherals still
active. In these states, power consumption can be
reduced even further, to as little as 4% of normal
operation requirements.
• Fail-Safe Clock Monitor: This option constantly
monitors the main clock source against a refer-
ence signal provided by the internal oscillator. If a
clock failure occurs, the controller is switched to
the internal oscillator block, allowing for continued
low-speed operation or a safe application
shutdown.
• On-the-Fly Mode Switching: The power-
managed modes are invoked by user code during
operation, allowing the user to incorporate
power-saving ideas into their application’s
software design.
• Low Consumption in Key Modules: The
power requirements for both Timer1 and the
Watchdog Timer are minimized. See
Section 26.0 “Electrical Characteristics”
for values.
• Two-Speed Start-up: This option allows the
internal oscillator to serve as the clock source
from Power-on Reset, or wake-up from Sleep
mode, until the primary clock source is available.
© 2008 Microchip Technology Inc.
DS39631E-page 7
MICROCHIP [ MICROCHIP ]
