Filter
Top Products
18049/8039
CRYSTAL OSCILLATOR MODE
LC
OSCILLATOR MODE
C1
~
2 XTAL1
I 1·6MH,
__
J.
__
C2
_-,-_~
c:=:::J
I
~
~
____
~:
______
~
______
~
XTAL2
C3
C1
= SpF ±
'hpF
+ STRAY <
5pF
C2 = CRYSTAL + STRAY <
8pF
C3 = 20pF ±
1pF
+ STRAY <
5pF
J:...
.£.
~
45
..
H
20
pF 5,2
MHz
120
...
H
20
pF
3.2
MHz
,.-.,.---''1
XT
AL1
'-
__
-.+
____
..,,3
XT
AL2
Cpp
:::
5 - 10
pF
PIN·TO·PIN
CAPACITANCE
CRYSTAL
SERIES
RESISTANCE
SHOULD
BE LESS
THAN
75\1
AT
8MHz; LESS
THAN
18011
AT 3.8MHz.
EACH C
SHOULD
BE
APPROXIMATELY
20
pF,
INCLUOING
STRAY
CAPACITANCE
DRIVING FROM EXTERNAL SOURCE
+ 5V
470Q
}>--i-----------=-j
x T
AL
1
+ 5V
470~,
'----'>----"-1
XTAL2
BE
HIGH
35·65%
OF
THE
PERIOD.
FOR XTAL 1
AND
XTAL 2 DEFINE
"HIGH"
AS
VOLTAGES
ABOVE
1.6V
AND
"LOW"
AS VOLTAGES
BELOW
1.8V. THE DUTY CYCLE REQUIREMENTS FOR EXTERNAL
LV
DRIVING XTAL 1
AND
XTAL 2 USING THE CIRCUIT
SHOWN
ABOVE ARE AS
FOLLOWS:
FOR
THE 8748, XTAL MUST
BE
HIGH
45·50% OF THE PERIOD
AND
XTAL 2 MUST
BE
HIGH
51).65%
OF
THE
PERIOD.
RISE
AND
FALL
TIMES MUST
NOT
EXCEED 20
ns.
FOR THE
8048,
XTAL 1 MUST BE HIGH 35·65%
OF
THE PERIOD
AND
XTAL 2 MUST
6-41
AFN·00737·07