Datasheet

PIC16HV540
DS40197B-page 32 Preliminary  2000 Microchip Technology Inc.
7.2 Oscillator Configurations
7.2.1 OSCILLATOR TYPES
The PIC16HV540 can be operated in four different
oscillator modes. The user can program two configura-
tion bits (FOSC1:FOSC0) to select one of these four
modes:
• LP: Low Power Crystal
• XT: Crystal/Resonator
• HS: High Speed Crystal/Resonator
• RC: Resistor/Capacitor
7.2.2 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 7-1). The
PIC16HV540 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 specifica-
tions. When in XT, LP or HS modes, the device can
have an external clock source drive the OSC1/CLKIN
pin (Figure 7-2).
FIGURE 7-1: CRYSTAL OPERATION
(OR CERAMIC RESONATOR)
(HS, XT OR LP OSC
CONFIGURATION)
FIGURE 7-2: EXTERNAL CLOCK INPUT
OPERATION (HS, XT OR LP
OSC CONFIGURATION)
TABLE 7-1: CAPACITOR SELECTION
FOR CERAMIC RESONATORS
- PIC16HV540
TABLE 7-2: CAPACITOR SELECTION
FOR CRYSTAL OSCILLATOR
- PIC16HV540
Note: Not all oscillator selections available for all
parts. See Section 7.1.
Note 1: See Capacitor Selection tables for
recommended values of C1 and C2.
2: A series resistor (RS) may be required for AT
strip cut crystals.
3: RF varies with the crystal chosen (approx.
value = 10 M
Ω).
C1
(1)
C2
(1)
XTAL
OSC2
OSC1
RF
(3)
SLEEP
To internal
logic
RS
(2)
PIC16HV540
Osc
Type
Resonator
Freq
Cap. Range
C1
Cap. Range
C2
XT 455 kHz
2.0 MHz
4.0 MHz
68-100 pF
15-33 pF
10-22 pF
68-100 pF
15-33 pF
10-22 pF
HS 8.0 MHz
16.0 MHz
10-22 pF
10 pF
10-22 pF
10 pF
Note: These values are for design guidance only.
Since each resonator has its own charac-
teristics, the user should consult the reso-
nator manufacturer for appropriate values
of external components.
Osc
Type
Resonator
Freq
Cap.Range
C1
Cap. Range
C2
LP 32 kHz
(1)
15 pF 15 pF
XT 100 kHz
200 kHz
455 kHz
1 MHz
2 MHz
4 MHz
15-30 pF
15-30 pF
15-30 pF
15-30 pF
15 pF
15 pF
200-300 pF
100-200 pF
15-100 pF
15-30 pF
15 pF
15 pF
HS 4 MHz
8 MHz
20 MHz
15 pF
15 pF
15 pF
15 pF
15 pF
15 pF
Note 1: For V
DD > 4.5V, C1 = C2 ≈ 30 pF is
recommended.
2: 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.
Note: If you change from this device to another
device, please verify oscillator characteris-
tics in your application.
Clock from
ext. system
OSC1
OSC2
PIC16HV540
Open