PIC18F45J10 FAMILY
TABLE 3-2:
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
3.3
External Clock Input (EC Modes)
The EC and ECPLL Oscillator modes require an exter-
nal clock source to be connected to the OSC1 pin.
There is no oscillator start-up time required after a
Power-on Reset or after an exit from Sleep mode.
Typical Capacitor Values
Crystal
Freq.
Tested:
Osc Type
C1
C2
In the EC Oscillator mode, the oscillator frequency
divided by 4 is available on the OSC2 pin. This signal
may be used for test purposes or to synchronize other
logic. Figure 3-2 shows the pin connections for the EC
Oscillator mode.
HS
4 MHz
8 MHz
20 MHz
27 pF
22 pF
15 pF
27 pF
22 pF
15 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.
FIGURE 3-2:
EXTERNAL CLOCK
INPUT OPERATION
(EC CONFIGURATION)
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.
OSC1/CLKI
Clock from
Ext. System
PIC18F45J10
OSC2/CLKO
See the notes following this table for additional
information.
FOSC/4
Crystals Used:
4 MHz
8 MHz
20 MHz
An external clock source may also be connected to the
OSC1 pin in the HS mode, as shown in Figure 3-3. In
this configuration, the divide-by-4 output on OSC2 is
not available.
FIGURE 3-3:
EXTERNAL CLOCK INPUT
OPERATION (HS OSC
CONFIGURATION)
Note 1: Higher capacitance 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
OSC1
Clock from
appropriate
components.
values
of
external
Ext. System
PIC18F45J10
(HS Mode)
OSC2
Open
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.
DS39682E-page 28
© 2009 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
