18049/8039

CRYSTAL OSCILLATOR MODE

LC OSCILLATOR MODE

C1

~ C2 ___-,JI-. ___~ c:=:::J1·6MH,

I

2 XTAL1

J:...

.£.

~

45 .. H

20 pF

5,2 MHz

120 ... H

20 pF

3.2 MHz

 

 

,.-.,.---''1 XT AL1

~~____~:______~______~ XTAL2

C3

C1 = SpF ± 'hpF+ STRAY < 5pF

C2 = CRYSTAL + STRAY < 8pF

C3 = 20pF ± 1pF + STRAY < 5pF

CRYSTAL SERIES RESISTANCE SHOULD BE LESS THAN 75\1 AT 8MHz; LESS THAN 18011 AT 3.8MHz.

' --.+____..,,3XT AL2

Cpp ::: 5 - 10 pF PIN·TO·PIN

 

CAPACITANCE

EACH C SHOULD BE APPROXIMATELY 20 pF, INCLUOING STRAY CAPACITANCE

DRIVING FROM EXTERNAL SOURCE

+5V

470Q

}>--i-----------

=-jxTAL 1

 

+ 5V

 

470~,

'----

'>----"-XTAL21

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 8048, XTAL 1 MUST BE HIGH 35·65% OF THE PERIOD AND XTAL 2 MUST

BE HIGH 35·65%OF THE PERIOD.

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.

6-41

AFN·00737·07

Page 190
Image 190
Intel mcs-48 manual Crystal Oscillator Mode LC Oscillator Mode, XT AL1