Cypress FS781, FS784, FS782 manual Soic

FS781/82/84

Crystal is 20 MHz is 1st Order with 18 pF load capacitance.

If Crystal load capacitance is different than 18 pF, C1 and C2 must be re-calculated.

For third overtone crystals, a parallel or series resonant trap is required.

Mount loop filter components as close to LF pin as possible.

C2
	1	Xin	VDD	8
	20 MHz
27 pF
	Y1
C3	2	Xout	S0	7

27 pF			FS781
			(SOIC)
	3	S1	FSOUT	6
	4	LF	VSS	5
	R6
C7	C8

**

**Occasionally, C8 is used to create a second pole for this loop filter. Refer to Loop Filter Selection

table. .

C1	VDD
	0.1 uF

FSOUT

Figure 5. FS781 Schematic

Document #: 38-07029 Rev. *F Page 7 of 12

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