PIC16C54-04SLASHP datasheet(26/84 Pages) MICROCHIP

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PIC16CR54C

DS40191A-page 26

Preliminary

7.2

Oscillator Conﬁgurations

7.2.1

OSCILLATOR TYPES

PIC16CR54Cs can be operated in four different

oscillator

modes.

The

user

can

program

two

conﬁguration bits (FOSC1: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/CLKIN and OSC2/CLKOUT

pins

establish

oscillation

(Figure 7-2).

The

PIC16CR54C 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 drive the

OSC1/CLKIN pin (Figure 7-3).

FIGURE 7-2:

CRYSTAL OPERATION

(OR CERAMIC RESONATOR)

(HS, XT OR LP OSC

CONFIGURATION)

Note 1: See Capacitor Selection tables for

recommended values of C1 and C2.

2: A series resistor (RS) may be required for

AT strip cut crystals.

3: RF varies with the crystal chosen (approx.

value = 10 M

Ω).

C1(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

SLEEP

To internal

logic

RS(2)

PIC16CR54C

FIGURE 7-3:

EXTERNAL CLOCK INPUT

OPERATION (HS, XT OR LP

OSC CONFIGURATION)

TABLE 7-1:

CAPACITOR SELECTION

FOR CERAMIC RESONATORS

- PIC16CR54C

TABLE 7-2:

CAPACITOR SELECTION

FOR CRYSTAL OSCILLATOR

- PIC16CR54C

Osc

Type

Resonator

Freq

Cap. Range

455 kHz

2.0 MHz

4.0 MHz

68-100 pF

15-33 pF

10-22 pF

68-100 pF

15-33 pF

10-22 pF

8.0 MHz

16.0 MHz

10-22 pF

10 pF

10-22 pF

10 pF

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.

Osc

Type

Resonator

Freq

Cap.Range

Cap. Range

32 kHz(1)

15 pF

100 kHz

200 kHz

455 kHz

1 MHz

2 MHz

4 MHz

15-30 pF

15 pF

200-300 pF

100-200 pF

15-100 pF

15-30 pF

15 pF

4 MHz

8 MHz

20 MHz

15 pF

Note 1: For VDD > 4.5V, C1 = C2

≈ 30 pF is

recommended.

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.

Note:

If you change from this device to

another device, please verify oscillator

characteristics in your application.

Clock from

ext. system

OSC1

OSC2

PIC16CR54C

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