Datasheet

 2010 Microchip Technology Inc. Preliminary DS39974A-page 37
PIC18F47J13 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.
FIGURE 3-2: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS OR HSPLL
CONFIGURATION)
TABLE 3-2: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
TABLE 3-3: CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
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.
Note: Use of a series resonant crystal may give
a frequency out of the crystal
manufacturer’s specifications.
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
V
DD 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
Note 1: See Table 3-2 and Table 3-3 for initial values
of C1 and C2.
2: R
S may be required to avoid overdriving
crystals with low drive level specifications.
C1
(1)
C2
(1)
XTAL
OSC2
OSC1
Sleep
To
Logic
R S
(2)
Internal
PIC18F47J13
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
V
DD 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 V
DD and temperature range that is
expected for the application.