Datasheet

 2010-2016 Microchip Technology Inc. DS40001412G-page 33
PIC18(L)F2X/4XK22
2.5.3 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 2-6). 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 MHz 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 2-6: QUARTZ CRYSTAL
OPERATION (LP, XT OR
HS MODE)
FIGURE 2-7: 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/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 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/CLKOUT