GMS81C5108
21. OSCILLATOR CIRCUIT
The GMS81C5108 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
21-1.
C1
C3
X
SX
OUT
OUT
C2
C4
4.19MHz
X
V
SX
IN
IN
32.768KHz
V
SS
SS
Recommend
Recommend
C3,C4 = 30pF
Crystal Oscillator
Ceramic Resonator
C1,C2 = 20pF
C1,C2 = 20pF
Crystal or Ceramic Oscillator
X
X
OUT
Open
X
X
OUT
R
EXT
Select R value according to AC Characteristics.
The Cap. is built in(5pF).
IN
External Clock
IN
External Oscillator
RC Oscillator
Figure 21-1 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.
In addition, see Figure 21-2 for the layout of the crystal.
X
X
OUT
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.
IN
Figure 21-2 Layout of Oscillator PCB circuit
80
JUNE 2001 Ver 1.0
HYNIX [ HYNIX SEMICONDUCTOR ]
