PIC18F44J10 datasheet(30/368 Pages) MICROCHIP

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PIC18F45J10 FAMILY

DS39682E-page 28

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:

4 MHz

27 pF

8 MHz

22 pF

20 MHz

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

VDD 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.

Since each resonator/crystal has its own

characteristics, the user should consult

the resonator/crystal manufacturer for

appropriate

values

external

components.

Rs may be required to avoid overdriving

crystals with low drive level specification.

Always verify oscillator performance over

the VDD and temperature range that is

expected for the application.

OSC1/CLKI

OSC2/CLKO

FOSC/4

Clock from

Ext. System

PIC18F45J10

OSC1

OSC2

Open

Clock from

Ext. System

PIC18F45J10

(HS Mode)

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