PIC16F631T-IP View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16F631T-IP

20-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

Microchip Technology 

PIC16F631/677/685/687/689/690

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 or high gain setting of 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 consumption

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)

PIC® MCU

C1

Quartz

Crystal

OSC1/CLKIN

RF(2)

To Internal

Logic

Sleep

C2

RS(1)

OSC2/CLKOUT

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

quartz crystals with low drive level.

2: The value of RF varies with the Oscillator mode

selected (typically between 2 MΩ to 10 MΩ).

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)

FIGURE 3-4:

CERAMIC RESONATOR

OPERATION

(XT OR HS MODE)

PIC® MCU

OSC1/CLKIN

C1

To Internal

Logic

RP(3)

RF(2)

Sleep

C2 Ceramic RS(1)

Resonator

OSC2/CLKOUT

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 MΩ to 10 MΩ).

3: An additional parallel feedback resistor (RP)

may be required for proper ceramic resonator

operation.

DS41262E-page 50

© 2008 Microchip Technology Inc.

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