PIC12F635ESS datasheet(40/234 Pages) MICROCHIP

40 / 234 page

PIC12F635/PIC16F636/639

DS41232D-page 38

3.4.3

LP, XT, HS MODES

The LP, XT and HS modes support the use of quartz

crystal resonators or ceramic resonators connected to

OSC1 and OSC2 (Figure 3-3). The mode selects a low,

medium

high

gain

setting

the

internal

inverter-amplifier to support various resonator types

and speed.

LP Oscillator mode selects the lowest gain setting of

the internal inverter-amplifier. LP mode current con-

sumption is the least of the three modes. This mode is

designed to drive only 32.768 kHz tuning-fork type

crystals (watch crystals).

XT Oscillator mode selects the intermediate gain

setting of the internal inverter-amplifier. XT mode

current consumption is the medium of the three modes.

This mode is best suited to drive resonators with a

medium drive level specification.

HS Oscillator mode selects the highest gain setting of the

internal inverter-amplifier. HS mode current consumption

is the highest of the three modes. This mode is best

suited for resonators that require a high drive setting.

Figure 3-3 and Figure 3-4 show typical circuits for

quartz crystal and ceramic resonators, respectively.

FIGURE 3-3:

QUARTZ CRYSTAL

OPERATION (LP, XT OR

HS MODE)

FIGURE 3-4:

CERAMIC RESONATOR

OPERATION

(XT OR HS MODE)

Note 1:

A series resistor (RS) may be required for

quartz crystals with low drive level.

The value of RF varies with the Oscillator mode

selected (typically between 2 M

Ω to 10 MΩ).

Quartz

RS(1)

OSC1/CLKIN

RF(2)

Sleep

To Internal

Logic

PIC® MCU

Crystal

OSC2/CLKOUT

Note 1: Quartz crystal characteristics vary according

to type, package and manufacturer. The

user should consult the manufacturer data

sheets for specifications and recommended

application.

2: Always verify oscillator performance over

the VDD and temperature range that is

expected for the application.

3: For oscillator design assistance, reference

the following Microchip Applications Notes:

• AN826, “Crystal Oscillator Basics and

Crystal Selection for rfPIC® and PIC®

Devices” (DS00826)

• AN849, “Basic PIC® Oscillator Design”

(DS00849)

• AN943, “Practical PIC® Oscillator

Analysis and Design” (DS00943)

• AN949, “Making Your Oscillator Work”

(DS00949)

Note

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

ceramic resonators with low drive level.

2: The value of RF varies with the Oscillator mode

selected (typically between 2 M

Ω to 10 MΩ).

3: An additional parallel feedback resistor (RP)

may be required for proper ceramic resonator

operation.

C2 Ceramic

RS(1)

OSC1/CLKIN

RF(2)

Sleep

To Internal

Logic

PIC® MCU

RP(3)

Resonator

OSC2/CLKOUT

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