GMS81C2012 datasheet(85/107 Pages) HYNIX

85 / 107 page

HYUNDAI MicroElectronics

GMS81C2012/GMS81C2020

MAR. 2000 Ver 1.00

18. OSCILLATOR CIRCUIT

The GMS81C20xx has two oscillation circuits internally.

XIN and XOUT are input and output for main frequency and

SXIN and SXOUT are input and output for sub frequency,

respectively, inverting amplifier which can be configured

for being used as an on-chip oscillator, as shown in Figure

18-1.

Figure 18-1 Oscillation Circuit

Oscillation circuit is designed to be used either with a ce-

ramic resonator or crystal oscillator. Since each crystal and

ceramic resonator have their own characteristics, the user

should consult the crystal manufacturer for appropriate

values of external components.

Oscillation circuit is designed to be used either with a ce-

ramic resonator or crystal oscillator. Since each crystal and

ceramic resonator have their own characteristics, the user

should consult the crystal manufacturer for appropriate

values of external components.

In addition, see Figure 18-2 for the layout of the crystal.

Note: Minimize the wiring length. Do not allow the wiring to

intersect with other signal conductors. Do not allow the wir-

ing to come near changing high current. Set the potential of

the grounding position of the oscillator capacitor to that of

VSS. Do not ground it to any ground pattern where high cur-

rent is present. Do not fetch signals from the oscillator.

Figure 18-2 Layout of Oscillator PCB circuit

XOUT

XIN

VSS

Recommend

C1,C2 = 20pF

XOUT

XIN

External Clock

Open

XOUT

XIN

External Oscillator

RC Oscillator (mask option)

Crystal or Ceramic Oscillator

SXOUT

SXIN

VSS

Recommend

C1,C2 = 100~120pF

32.768KHz

4.19MHz

Crystal Oscillator

Ceramic Resonator

C1,C2 = 30pF

Refer to AC Characteristics

For selection R value,

REXT

XOUT

XIN

GMS81C2012 Datasheet(PDF) 85 Page - Hynix Semiconductor

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