PIC16C72-02E/SP View Datasheet(PDF) - Microchip Technology
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PIC16C72-02E/SP Datasheet PDF : 124 Pages
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PIC16C72 Series
10.2 Oscillator Configurations
10.2.1 OSCILLATOR TYPES
The PIC16CXXX family can be operated in four differ-
ent oscillator modes. The user can program two config-
uration bits (FOSC1 and FOSC0) to select one of these
four modes:
• LP
• XT
• HS
• RC
Low Power Crystal
Crystal/Resonator
High Speed Crystal/Resonator
Resistor/Capacitor
10.2.2 CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In XT, LP or HS modes a crystal or ceramic resonator
is connected to the OSC1/CLKIN and OSC2/CLKOUT
pins to establish oscillation (Figure 10-2). The
PIC16CXXX family 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 spec-
ifications. When in XT, LP or HS modes, the device can
have an external clock source to drive the OSC1/
CLKIN pin (Figure 10-3).
FIGURE 10-2: CRYSTAL/CERAMIC
RESONATOR OPERATION
(HS, XT OR LP
OSC CONFIGURATION)
C1(1)
OSC1
XTAL
OSC2
RS(2)
C2(1)
RF(3)
To
internal
logic
SLEEP
PIC16CXXX
Note1:
2:
3:
See Table 10-1 and Table 10-2 for recom-
mended values of C1 and C2.
A series resistor (RS) may be required for
AT strip cut crystals.
RF varies with the crystal chosen.
FIGURE 10-3: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
Clock from
ext. system
Open
OSC1
PIC16CXXX
OSC2
TABLE 10-1 CERAMIC RESONATORS
Ranges Tested:
Mode
Freq
OSC1
OSC2
XT
455 kHz 68 - 100 pF 68 - 100 pF
2.0 MHz 15 - 68 pF 15 - 68 pF
4.0 MHz 15 - 68 pF 15 - 68 pF
HS
8.0 MHz 10 - 68 pF 10 - 68 pF
16.0 MHz 10 - 22 pF 10 - 22 pF
These values are for design guidance only. See
notes at bottom of page.
Resonators Used:
455 kHz Panasonic EFO-A455K04B ± 0.3%
2.0 MHz Murata Erie CSA2.00MG ± 0.5%
4.0 MHz Murata Erie CSA4.00MG ± 0.5%
8.0 MHz Murata Erie CSA8.00MT ± 0.5%
16.0 MHz Murata Erie CSA16.00MX ± 0.5%
All resonators used did not have built-in capacitors.
TABLE 10-2 CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR
Osc Type
Crystal
Freq
Cap. Range Cap. Range
C1
C2
LP
32 kHz
33 pF
33 pF
200 kHz
15 pF
15 pF
XT
200 kHz
47-68 pF
47-68 pF
1 MHz
15 pF
15 pF
4 MHz
15 pF
15 pF
HS
4 MHz
15 pF
15 pF
8 MHz
15-33 pF
15-33 pF
20 MHz
15-33 pF
15-33 pF
These values are for design guidance only. See
notes at bottom of page.
Crystals Used
32 kHz Epson C-001R32.768K-A
± 20 PPM
200 kHz STD XTL 200.000KHz
± 20 PPM
1 MHz ECS ECS-10-13-1
± 50 PPM
4 MHz ECS ECS-40-20-1
± 50 PPM
8 MHz EPSON CA-301 8.000M-C ± 30 PPM
20 MHz EPSON CA-301 20.000M-C ± 30 PPM
Note 1: Recommended values of C1 and C2 are
identical to the ranges tested (Table 10-1).
2: Higher capacitance increases the stability
of oscillator but also increases the start-up
time.
3: Since each resonator/crystal has its own
characteristics, the user should consult the
resonator/crystal manufacturer for appropri-
ate values of external components.
4: Rs may be required in HS mode as well as
XT mode to avoid overdriving crystals with
low drive level specification.
DS39016A-page 60
Preliminary
© 1998 Microchip Technology Inc.
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