PIC18F23K20 Datasheet, PDF (31/420 Pages) Microchip Technology – 28/40/44-Pin Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

2.4.3 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 2-3). 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 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 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 2-3 and Figure 2-4 show typical circuits for
quartz crystal and ceramic resonators, respectively.
FIGURE 2-3:
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).
PIC18F2XK20/4XK20
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 2-4:
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.
© 2007 Microchip Technology Inc.
Advance Information
DS41303B-page 29