RFPIC12C509AF datasheet(46/104 Pages) MICROCHIP

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rfPIC12C509AG/509AF

DS70031A-page 44

Preliminary

8.2

Oscillator Configurations

8.2.1

OSCILLATOR TYPES

The oscillator frequency is a primary factor in determin-

ing PICmicro microcontroller unit (MCU) current draw.

As a rough guideline, the rfPIC12C509AG/509AF

draws approximately 250

µA per MHz.

The rfPIC12C509AG/509AF 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

• INTRC: Internal 4 MHz Oscillator

• EXTRC: External Resistor/Capacitor

8.2.2

CRYSTAL OSCILLATOR / CERAMIC

RESONATORS

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

connected to the GP5/OSC1/CLKIN and GP4/OSC2

pins

establish

oscillation

(Figure 8-2).

The

rfPIC12C509AG/509AF 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 or LP modes, the device

can have an external clock source drive the GP5/

OSC1/CLKIN pin (Figure 8-3).

FIGURE 8-2:

CRYSTAL OPERATION (OR

CERAMIC RESONATOR)

(XT OR LP OSC

CONFIGURATION)

FIGURE 8-3:

EXTERNAL CLOCK INPUT

OPERATION (XT OR LP OSC

CONFIGURATION)

TABLE 8-1:

CAPACITOR SELECTION

FOR CERAMIC RESONATORS

- rfPIC12C509AG/509AF

TABLE 8-2:

CAPACITOR SELECTION

FOR CRYSTAL OSCILLATOR -

rfPIC12C509AG/509AF

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 approximate value = 10 M

Ω.

(1)

C2(1)

XTAL

OSC2

OSC1

RF(3)

SLEEP

To internal

logic

RS(2)

rfPIC12C509AG/509AF

Osc

Type

Resonator

Freq

Cap. Range

4.0 MHz

30 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

200 kHz

1MHz

4MHz

47-68 pF

15 pF

47-68 pF

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 to avoid overdriving crystals with low

drive level specification. Since each crystal has its

own characteristics, the user should consult the crys-

tal manufacturer for appropriate values of external

components.

Clock from

ext. system

OSC1

OSC2

Open

rfPIC12C509AG/509AF

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