Datasheet

 2003 Microchip Technology Inc. DS30235J-page 47
PIC16C62X
9.2 Oscillator Configurations
9.2.1 OSCILLATOR TYPES
The PIC16C62X devices can be operated in four
different oscillator options. The user can program two
configuration bits (FOSC1 and FOSC0) to select one of
these four modes:
• LP Low Power Crystal
• XT Crystal/Resonator
• HS High Speed Crystal/Resonator
• RC Resistor/Capacitor
9.2.2 CRYSTAL OSCILLATOR / CERAMIC
RESONATORS
In XT, LP or HS modes, a crystal or ceramic resonator
is connected to the OSC1 and OSC2 pins to establish
oscillation (Figure 9-1). The PIC16C62X oscillator
design requires the use of a parallel cut crystal. Use of
a series cut crystal may give a frequency out of the
crystal manufacturers specifications. When in XT, LP or
HS modes, the device can have an external clock
source to drive the OSC1 pin (Figure 9-2).
FIGURE 9-1: CRYSTAL OPERATION
(OR CERAMIC
RESONATOR) (HS, XT OR
LP OSC
CONFIGURATION)
FIGURE 9-2: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR
LP OSC
CONFIGURATION)
TABLE 9-1: CAPACITOR SELECTION FOR
CERAMIC RESONATORS
TABLE 9-2: CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
See Table 9-1 and Table 9-2 for recommended
values of C1 and C2.
Note: A series resistor may be required for
AT strip cut crystals.
C1
C2
XTAL
OSC2
RS
OSC1
RF
SLEEP
To internal logic
PIC16C62X
See Note
clock from
ext. system
PIC16C62X
OSC1
OSC2
Open
Ranges Characterized:
Mode Freq OSC1(C1) OSC2(C2)
XT 455 kHz
2.0 MHz
4.0 MHz
22 - 100 pF
15 - 68 pF
15 - 68 pF
22 - 100 pF
15 - 68 pF
15 - 68 pF
HS 8.0 MHz
16.0 MHz
10 - 68 pF
10 - 22 pF
10 - 68 pF
10 - 22 pF
Higher capacitance increases the stability of the oscil-
lator but also increases the start-up time. These
values are for design guidance only. Since each
resonator has its own characteristics, the user
should consult the resonator manufacturer for
appropriate values of external components.
Mode Freq OSC1(C1) OSC2(C2)
LP
32 kHz
200 kHz
68 - 100 pF
15 - 30 pF
68 - 100 pF
15 - 30 pF
XT
100 kHz
2 MHz
4 MHz
68 - 150 pF
15 - 30 pF
15 - 30 pF
150 - 200 pF
15 - 30 pF
15 - 30 pF
HS
8 MHz
10 MHz
20 MHz
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
15 - 30 pF
Higher capacitance increases the stability of the
oscillator but also increases the start-up time.
These values are for design guidance only. Rs may
be required in HS mode as well as XT mode to
avoid overdriving crystals with low drive level
specification. Since each crystal has its own
characteristics, the user should consult the crystal
manufacturer for appropriate values of external
components.