PIC16F688

Manufacturer Part NumberPIC16F688
ManufacturerMicrochip Technology Inc.
PIC16F688 datasheet
 
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Page 26/202:

CERAMIC RESONATOR OPERATION

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PIC16F688
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 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.
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
OSC1/CLKIN
C1
Quartz
(2)
R
F
Crystal
OSC2/CLKOUT
(1)
C2
R
S
Note 1: A series resistor (R
) may be required for
S
quartz crystals with low drive level.
2: The value of R
varies with the Oscillator mode
F
selected (typically between 2 MΩ to 10 MΩ).
DS41203D-page 24
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
expected for the application.
3: For oscillator design assistance, reference
the following Microchip Applications Notes:
• AN826, “Crystal Oscillator Basics and
Crystal Selection for rfPIC
Devices” (DS00826)
• AN849, “Basic PIC
(DS00849)
• AN943, “Practical PIC
Analysis and Design” (DS00943)
• AN949, “Making Your Oscillator Work”
(DS00949)
FIGURE 3-4:
C1
To Internal
Logic
C2 Ceramic
Resonator
Sleep
Note 1: A series resistor (R
ceramic resonators with low drive level.
2: The value of R
selected (typically between 2 MΩ to 10 MΩ).
3: An additional parallel feedback resistor (R
may be required for proper ceramic resonator
operation.
and temperature range that is
DD
®
®
and PIC
®
Oscillator Design”
®
Oscillator
CERAMIC RESONATOR
OPERATION
(XT OR HS MODE)
®
PIC
MCU
OSC1/CLKIN
To Internal
Logic
(3)
R
(2)
P
R
Sleep
F
OSC2/CLKOUT
(1)
R
S
) may be required for
S
varies with the Oscillator mode
F
)
P
© 2007 Microchip Technology Inc.