PIC18F47J53 Datasheet, PDF (37/586 Pages) Microchip Technology – 28/44-Pin, High-Performance USB Microcontrollers with nanoWatt XLP Technology

PIC18F47J53 FAMILY
3.2.2
CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In HS and HSPLL Oscillator modes, a crystal or
ceramic resonator is connected to the OSC1 and
OSC2 pins to establish oscillation. Figure 3-2 displays
the pin connections.
The oscillator design requires the use of a parallel
resonant crystal.
Note:
Use of a series resonant crystal may give
a frequency out of the crystal
manufacturer’s specifications.
FIGURE 3-2:
CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS OR HSPLL
CONFIGURATION)
C1⁽¹⁾
OSC1
XTAL
To
Internal
Logic
RS⁽²⁾
C2⁽¹⁾
OSC2
Sleep
PIC18F47J53
Note 1:
2:
See Table 3-2 and Table 3-3 for initial values
of C1 and C2.
RS may be required to avoid overdriving
crystals with low drive level specifications.
TABLE 3-2: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Typical Capacitor Values Used:
Mode
Freq
OSC1
OSC2
HS
8.0 MHz
16.0 MHz
27 pF
22 pF
27 pF
22 pF
Capacitor values are for design guidance only.
These capacitors were tested with the resonators
listed below for basic start-up and operation. These
values are not optimized.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
VDD and temperature range for the application.
See the notes following Table 3-3 for additional
information.
Resonators Used:
4.0 MHz
8.0 MHz
16.0 MHz
TABLE 3-3: CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
Osc Type
Crystal
Freq
Typical Capacitor Values
Tested:
C1
C2
HS
4 MHz
27 pF
27 pF
8 MHz
22 pF
22 pF
16 MHz
18 pF
18 pF
Capacitor values are for design guidance only.
These capacitors were tested with the crystals listed
below for basic start-up and operation. These values
are not optimized.
Different capacitor values may be required to produce
acceptable oscillator operation. The user should test
the performance of the oscillator over the expected
VDD and temperature range for the application.
See the notes following this table for additional
information.
Crystals Used:
4 MHz
8 MHz
16 MHz
Note 1: Higher capacitance not only increases
the stability of oscillator, but also
increases the start-up time.
2: Since each resonator/crystal has its own
characteristics, the user should consult
the resonator/crystal manufacturer for
appropriate values of external
components.
3: Rs may be required to avoid overdriving
crystals with low drive level specification.
4: Always verify oscillator performance over
the VDD and temperature range that is
expected for the application.
An internal postscaler allows users to select a clock
frequency other than that of the crystal or resonator.
Frequency division is determined by the CPDIV
Configuration bits. Users may select a clock frequency
of the oscillator frequency, or 1/2, 1/3 or 1/6 of the
frequency.
 2010 Microchip Technology Inc.
Preliminary
DS39964B-page 37