PIC16F684-ESLASHST datasheet(23/164 Pages) MICROCHIP

23 / 164 page

 2004 Microchip Technology Inc.

Preliminary

DS41202C-page 21

PIC16F684

3.3.3

LP, XT, HS MODES

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

crystal resonators or ceramic resonators connected to

the OSC1 and OSC2 pins (Figure 3-1). 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 con-

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

best suited to drive resonators with a low drive level

specification, for example, tuning fork type 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,

for

example,

low-frequency/AT-cut quartz crystal resonators.

HS Oscillator mode selects the highest gain setting of

the

internal

inverter-amplifier.

mode

current

consumption is the highest of the three modes. This

mode is best suited for resonators that require a high

drive

setting,

for example,

high-frequency/AT-cut

quartz crystal resonators or ceramic resonators.

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: Quartz

crystal

characteristics

vary

according to type, package and manufac-

turer. The user should consult the manu-

facturer data sheets for specifications and

recommended application.

2: Always verify oscillator performance over

the VDD and temperature range that is

expected for the application.

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 M

Ω).

Quartz

OSC2

RS(1)

OSC1

RF(2)

Sleep

To Internal

Logic

PIC16F684

Crystal

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 M

Ω).

3: An additional parallel feedback resistor (RP)

may be required for proper ceramic resonator

operation (typical value 1 M

Ω).

Ceramic

OSC2

RS(1)

OSC1

RF(2)

Sleep

To Internal

Logic

PIC16F684

RP(3)

Resonator

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