Datasheet

PIC18(L)F2X/45K50
DS30684A-page 38  2012 Microchip Technology Inc.
3.5.3 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 3-5). 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 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.
HS Oscillator mode offers a Medium Power (MP) and a
High Power (HP) option selectable by the FOSC<3:0>
bits. The MP selections are best suited for oscillator
frequencies between 4 and 16 MHz. The HP selection
has the highest gain setting of the internal inverter-
amplifier and is best suited for frequencies above
16 MHz. HS mode is best suited for resonators that
require a high drive setting.
FIGURE 3-5: QUARTZ CRYSTAL
OPERATION (LP, XT OR
HS MODE)
FIGURE 3-6: CERAMIC RESONATOR
OPERATION
(XT OR HS MODE)
Note 1: A series resistor (RS) may be required for
quartz crystals with low drive level.
2: The value of R
F varies with the Oscillator mode
selected (typically between 2 M to 10 M.
C1
C2
Quartz
R
S
(1)
OSC1/CLKIN
RF
(2)
Sleep
To Internal
Logic
PIC
®
MCU
Crystal
OSC2/CLKO
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 V
DD and temperature range that is
expected for the application.
3: For oscillator design assistance, refer to the
following Microchip Application 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 R
F varies with the Oscillator mode
selected (typically between 2 M to 10 M.
3: An additional parallel feedback resistor (R
P)
may be required for proper ceramic resonator
operation.
C1
C2
Ceramic
R
S
(1)
OSC1/CLKIN
RF
(2)
Sleep
To Internal
Logic
PIC
®
MCU
RP
(3)
Resonator
OSC2/CLKO