PIC17C75X Datasheet, PDF (16/320 Pages) Microchip Technology – High-Performance 8-Bit CMOS EPROM Microcontrollers

PIC17C75X
FIGURE 4-2:
CRYSTAL OR CERAMIC
RESONATOR OPERATION (XT
OR LF OSC CONFIGURATION)
OSC1
C1
XTAL
RF
SLEEP
OSC2
Note1
C2
PIC17CXXX
To internal
logic
See Table 4-1 and Table 4-2 for recommended values of
C1 and C2.
Note 1: A series resistor (Rs) may be required for
AT strip cut crystals.
TABLE 4-1:
CAPACITOR SELECTION
FOR CERAMIC
RESONATORS
Oscillator
Type
Resonator
Frequency
Capacitor Range
C1 = C2 ⁽¹⁾
LF
455 kHz
15 - 68 pF
2.0 MHz
10 - 33 pF
XT
4.0 MHz
22 - 68 pF
8.0 MHz
33 - 100 pF
16.0 MHz
33 - 100 pF
Higher capacitance increases the stability of the oscillator
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 manu-
facturer for appropriate values of external components.
Note 1: These values include all board capaci-
tances on this pin. Actual capacitor value
depends on board capacitance
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%
Resonators used did not have built-in capacitors.
FIGURE 4-3:
CRYSTAL OPERATION,
OVERTONE CRYSTALS (XT
OSC CONFIGURATION)
C1
OSC1
C2
OSC2
SLEEP
0.1 µF
PIC17CXXX
To filter the fundamental frequency
1
LC2
=
(2πf)²
Where f = tank circuit resonant frequency. This should be
midway between the fundamental and the 3rd overtone
frequencies of the crystal.
TABLE 4-2: CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
Osc
Type
Freq
C1 ⁽³⁾
C2 ⁽³⁾
LF
32 kHz⁽¹⁾ 100-150 pF 100-150 pF
1 MHz 10-33 pF
10-33 pF
2 MHz 10-33 pF
10-33 pF
XT
2 MHz 47-100 pF
4 MHz
8 MHz ⁽²⁾
15-68 pF
15-47 pF
16 MHz
TBD
25 MHz 15-47 pF
32 MHz ⁽³⁾
10
47-100 pF
15-68 pF
15-47 pF
TBD
15-47 pF
10
Higher capacitance increases the stability of the oscillator
but also increases the start-up time and the oscillator cur-
rent. These values are for design guidance only. RS may be
required in XT mode to avoid overdriving the crystals with
low drive level specification. Since each crystal has its own
characteristics, the user should consult the crystal manufac-
turer for appropriate values for external components.
Note 1: For VDD > 4.5V, C1 = C2 ≈ 30 pF is recom-
mended.
2: RS of 330Ω is required for a capacitor com-
bination of 15/15 pF.
3: These values include all board capaci-
tances on this pin. Actual capacitor value
depends on board capacitance
Crystals Used:
32.768 kHz
1.0 MHz
2.0 MHz
4.0 MHz
8.0 MHz
16.0 MHz
25 MHz
32 MHz
Epson C-001R32.768K-A
ECS-10-13-1
ECS-20-20-1
ECS-40-20-1
ECS ECS-80-S-4
ECS-80-18-1
ECS-160-20-1
CTS CTS25M
CRYSTEK HF-2
± 20 PPM
± 50 PPM
± 50 PPM
± 50 PPM
± 50 PPM
TBD
± 50 PPM
± 50 PPM
DS30264A-page 16
Preliminary
© 1997 Microchip Technology Inc.