Datasheet

PIC18F45J10 FAMILY
DS39682E-page 28 © 2009 Microchip Technology Inc.
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.
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.
FIGURE 3-2: EXTERNAL CLOCK
INPUT OPERATION
(EC CONFIGURATION)
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)
Osc Type
Crystal
Freq.
Typical Capacitor Values
Tested:
C1 C2
HS 4 MHz 27 pF 27 pF
8 MHz 22 pF 22 pF
20 MHz 15 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.
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
20 MHz
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
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.
OSC1/CLKI
OSC2/CLKO
F
OSC/4
Clock from
Ext. System
PIC18F45J10
OSC1
OSC2
Open
Clock from
Ext. System
PIC18F45J10
(HS Mode)