PIC18FXX20
TABLE 2-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
2.0
2.1
OSCILLATOR
CONFIGURATIONS
Ranges Tested:
Oscillator Types
Mode
XT
Freq
C1
C2
The PIC18FXX20 devices can be operated in eight dif-
ferent Oscillator modes. The user can program three
configuration bits (FOSC2, FOSC1, and FOSC0) to
select one of these eight modes:
1. LP
2. XT
455 kHz
2.0 MHz
4.0 MHz
8.0 MHz
16.0 MHz
68 - 100 pF 68 - 100 pF
15 - 68 pF
15 - 68 pF
15 - 68 pF
15 - 68 pF
10 - 68 pF
10 - 22 pF
HS
10 - 68 pF
10 - 22 pF
Low Power Crystal
Crystal/Resonator
High Speed Crystal/Resonator
High Speed Crystal/Resonator
with PLL enabled
External Resistor/Capacitor
External Resistor/Capacitor with
I/O pin enabled
External Clock
External Clock with I/O pin
enabled
These values are for design guidance only.
3. HS
4. HS+PLL
See notes following this table.
Resonators Used:
455 kHz Panasonic EFO-A455K04B
2.0 MHz Murata Erie CSA2.00MG
4.0 MHz Murata Erie CSA4.00MG
8.0 MHz Murata Erie CSA8.00MT
16.0 MHz Murata Erie CSA16.00MX
± 0.3%
5. RC
6. RCIO
± 0.5%
± 0.5%
± 0.5%
± 0.5%
7. EC
8. ECIO
All resonators used did not have built-in capacitors.
2.2
Crystal Oscillator/Ceramic
Resonators
Note 1: Higher capacitance increases the stability
of the oscillator, but also increases the
start-up time.
In XT, LP, HS or HS+PLL Oscillator modes, a crystal or
ceramic resonator is connected to the OSC1 and
OSC2 pins to establish oscillation. Figure 2-1 shows
the pin connections.
The PIC18FXX20 oscillator design requires the use of
a parallel cut crystal.
2: When operating below 3V VDD, or when
using certain ceramic resonators at any
voltage, it may be necessary to use high
gain HS mode, try a lower frequency
resonator, or switch to a crystal oscillator.
3: Since each resonator/crystal has its own
characteristics, the user should consult the
resonator/crystal manufacturer for appro-
priate values of external components, or
verify oscillator performance.
Note: Use of a series cut crystal may give a fre-
quency out of the crystal manufacturer’s
specifications.
FIGURE 2-1:
CRYSTAL/CERAMIC
RESONATOROPERATION
(HS, XT OR LP
CONFIGURATION)
(1)
C1
OSC1
To
Internal
Logic
(3)
RF
XTAL
SLEEP
(2)
RS
(1)
C2
PIC18FXX20
OSC2
Note 1: See Table 2-1 and Table 2-2 for recommended
values of C1 and C2.
2: A series resistor (RS) may be required for AT
strip cut crystals.
3: RF varies with the Oscillator mode chosen.
2003 Microchip Technology Inc.
Advance Information
DS39609A-page 21
MICROCHIP [ MICROCHIP ]
