DM163006 datasheet(22/320 Pages) MICROCHIP

22 / 320 page

PIC18C601/801

DS39541A-page 22

Advance Information

 2001 Microchip Technology Inc.

TABLE 2-1:

CERAMIC RESONATORS

TABLE 2-2:

CAPACITOR SELECTION FOR

CRYSTAL OSCILLATOR

2.3

RC Oscillator

For timing insensitive applications, the "RC" oscillator

mode offers additional cost savings. The RC oscillator

frequency is a function of the supply voltage, the resis-

tor (REXT) and capacitor (CEXT) values and the operat-

ing temperature. In addition to this, the oscillator

frequency will vary from unit to unit due to normal pro-

cess parameter variation. Furthermore, the difference

in lead frame capacitance between package types will

also affect the oscillation frequency, especially for low

CEXT values. The user also needs to take into account

variation due to tolerance of external R and C compo-

nents used. Figure 2-2 shows how the RC combination

is connected.

In the RC oscillator mode, the oscillator frequency

divided by 4 is available on the OSC2 pin. This signal

may be used for test purposes or to synchronize other

logic.

FIGURE 2-2:

RC OSCILLATOR MODE

Ranges Tested:

Mode

Freq.

OSC1

OSC2

8.0 MHz

16.0 MHz

20.0 MHz

25.0 MHz

10 - 68 pF

10 - 22 pF

TBD

10 - 68 pF

10 - 22 pF

TBD

HS+PLL

4.0 MHz

TBD

These values are for design guidance only.

See notes on this page.

Resonators Used:

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.

Osc Type

Crystal

Freq.

Cap. Range

32.0 kHz

33 pF

200 kHz

15 pF

4.0 MHz

15 pF

8.0 MHz

15-33 pF

20.0 MHz

15-33 pF

25.0 MHz

TBD

HS+PLL

4.0 MHz

15 pF

These values are for design guidance only.

See notes on this page.

Crystals Used

32.0 kHz

Epson C-001R32.768K-A

± 20 PPM

200 kHz

STD XTL 200.000kHz

± 20 PPM

1.0 MHz

ECS ECS-10-13-1

± 50 PPM

4.0 MHz

ECS ECS-40-20-1

± 50 PPM

8.0 MHz

EPSON CA-301 8.000M-C

± 30 PPM

20.0 MHz EPSON CA-301 20.000M-C

± 30 PPM

Note 1: Recommended values of C1 and C2 are

identical to the ranges tested (Table 2-1).

2: Higher capacitance increases the stability

of the 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 appro-

priate values of external components.

4: Rs may be required in HS mode to avoid

overdriving crystals with low drive level

specification.

OSC2/CLKO

CEXT

REXT

OSC1

FOSC/4

Internal

Clock

VDD

VSS

Recommended values:

3 k

Ω ≤ REXT ≤ 100 kΩ

CEXT > 20pF

or I/O

PIC18C601/801

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