PIC16C620 datasheet(49/128 Pages) MICROCHIP

49 / 128 page

 2003 Microchip Technology Inc.

DS30235J-page 47

PIC16C62X

9.2

Oscillator Configurations

9.2.1

OSCILLATOR TYPES

The PIC16C62X devices can be operated in four

different oscillator options. The user can program two

configuration bits (FOSC1 and FOSC0) to select one of

these four modes:

• LP

Low Power Crystal

• XT

Crystal/Resonator

• HS

High Speed Crystal/Resonator

• RC

Resistor/Capacitor

9.2.2

CRYSTAL OSCILLATOR / CERAMIC

RESONATORS

In XT, LP or HS modes, a crystal or ceramic resonator

is connected to the OSC1 and OSC2 pins to establish

oscillation (Figure 9-1). The PIC16C62X oscillator

design requires the use of a parallel cut crystal. Use of

a series cut crystal may give a frequency out of the

crystal manufacturers specifications. When in XT, LP or

HS modes, the device can have an external clock

source to drive the OSC1 pin (Figure 9-2).

FIGURE 9-1:

CRYSTAL OPERATION

(OR CERAMIC

RESONATOR) (HS, XT OR

LP OSC

CONFIGURATION)

FIGURE 9-2:

EXTERNAL CLOCK INPUT

OPERATION (HS, XT OR

LP OSC

CONFIGURATION)

TABLE 9-1:

CAPACITOR SELECTION FOR

CERAMIC RESONATORS

TABLE 9-2:

CAPACITOR SELECTION FOR

CRYSTAL OSCILLATOR

See Table 9-1 and Table 9-2 for recommended

values of C1 and C2.

Note:

A series resistor may be required for

AT strip cut crystals.

XTAL

OSC2

OSC1

SLEEP

To internal logic

PIC16C62X

See Note

clock from

ext. system

PIC16C62X

OSC1

OSC2

Open

Ranges Characterized:

Mode

Freq

OSC1(C1)

OSC2(C2)

455 kHz

2.0 MHz

4.0 MHz

22 - 100 pF

15 - 68 pF

22 - 100 pF

15 - 68 pF

8.0 MHz

16.0 MHz

10 - 68 pF

10 - 22 pF

10 - 68 pF

10 - 22 pF

Higher capacitance increases the stability of the oscil-

lator but also increases the start-up time. These

values are for design guidance only. Since each

resonator has its own characteristics, the user

should consult the resonator manufacturer for

appropriate values of external components.

Mode

Freq

OSC1(C1)

OSC2(C2)

32 kHz

200 kHz

68 - 100 pF

15 - 30 pF

68 - 100 pF

15 - 30 pF

100 kHz

2 MHz

4 MHz

68 - 150 pF

15 - 30 pF

150 - 200 pF

15 - 30 pF

8 MHz

10 MHz

20 MHz

15 - 30 pF

Higher capacitance increases the stability of the

oscillator but also increases the start-up time.

These values are for design guidance only. Rs may

be required in HS mode as well as XT mode to

avoid overdriving crystals with low drive level

specification. Since each crystal has its own

characteristics, the user should consult the crystal

manufacturer for appropriate values of external

components.

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