PIC16LC554 datasheet(37/96 Pages) MICROCHIP

37 / 96 page

Preliminary

DS40143B-page 37

PIC16C55X(A)

7.2

Oscillator Conﬁgurations

7.2.1

OSCILLATOR TYPES

The PIC16C55X(A) 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

7.2.2

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 7-2). The PIC16C55X(A) 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 7-3).

FIGURE 7-2:

CRYSTAL OPERATION

(OR CERAMIC RESONATOR)

(HS, XT OR LP OSC

CONFIGURATION)

FIGURE 7-3:

EXTERNAL CLOCK INPUT

OPERATION (HS, XT OR LP

OSC CONFIGURATION)

See Table 7-1 and Table 7-2 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

PIC16C55X(A)

see Note

Clock from

ext. system

PIC16C55X(A)

OSC1

OSC2

Open

TABLE 7-1:

CAPACITOR SELECTION

FOR CERAMIC RESONATORS

(PRELIMINARY)

TABLE 7-2:

CAPACITOR SELECTION

FOR CRYSTAL OSCILLATOR

(PRELIMINARY)

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 oscillator

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 man-

ufacturer for appropriate values of external components.

Resonators to be Characterized:

455 kHz

Panasonic EFO-A455K04B

±0.3%

2.0 MHz

Murata Erie CSA2.00MG

±0.5%

4.0 MHz

Murata Erie CSA4.00MG

±0.5%

8.0 MHz

Murata Erie CSA8.00MT

±0.5%

16.0 MHz

Murata Erie CSA16.00MX

±0.5%

All resonators used did not have built-in capacitors.

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 manu-

facturer for appropriate values of external components.

Crystals to be Characterized:

32.768 kHz

Epson C-001R32.768K-A

± 20 PPM

100 kHz

Epson C-2 100.00 KC-P

± 20 PPM

200 kHz

STD XTL 200.000 kHz

± 20 PPM

2.0 MHz

ECS ECS-20-S-2

± 50 PPM

4.0 MHz

ECS ECS-40-S-4

± 50 PPM

10.0 MHz

ECS ECS-100-S-4

± 50 PPM

20.0 MHz

ECS ECS-200-S-4

± 50 PPM

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